Two iPhones and an app will do the job of a dedicated baby monitor, and for most families they do it better. The camera and microphone in a five-year-old iPhone beat what you get in a £150 monitor, the screen is far better, and alerts follow you anywhere you have signal instead of stopping where a 2.4 GHz radio stops.

That is the pitch. This guide covers what the pitch leaves out: what the setup actually requires, which features matter at 2am, what a dedicated camera still does better, and what it costs.

What an iPhone baby monitor app is

An iPhone baby monitor app turns two Apple devices into a monitor. One iPhone or iPad stays in the nursery as the camera, called the baby unit. The other stays with you as the viewer, called the parent unit. They pair once by QR code, then stream live video and audio to each other over Wi-Fi or cellular. There is no dedicated hardware to buy and nothing to store in a cupboard afterwards.

That is the whole category. Implementations differ far more than the App Store screenshots suggest, and the rest of this guide is about how.

What you need

Two devices, and they have to be reasonably modern.

Both must run iOS 17 or later. In practice that means an iPhone XS or newer, or an iPad from roughly 2018 onwards. This is the constraint people get wrong most often. Plenty of guides say "iPhone 8 or later", but the iPhone 8 stops at iOS 16 and cannot run any of this.
The baby unit does not need a SIM, a phone plan, or an intact screen. It needs a working camera, a working microphone and a way onto the internet. A cracked-screen phone in a drawer makes a perfectly good baby unit, because you never look at its screen again after setup.
A charging cable and a socket near the cot. Not optional, for reasons covered below.
Something to hold it at the right angle. A gooseneck clamp on a shelf costs a few pounds and holds the angle permanently.

If you only own one spare device, a partner's phone is the second unit. It does not need its own subscription; family sharing is covered further down.

Setting it up

The whole flow fits in a paragraph.

Install MonitorUltra on both devices. On first launch each one asks which role it plays. The nursery device becomes the baby unit and displays a QR code. The parent unit scans it. That is pairing in full: no account to create on the baby unit, no code to type, nothing to configure on your router, no port forwarding. The two devices remember each other and reconnect on their own the next night.

Deciding where the camera goes takes longer, and it matters more than which app you pick. A £200 camera aimed badly tells you less than a five-year-old phone aimed well. The short version: mount it 1.5 to 2 m up, angle it down so the whole mattress is in frame instead of zooming in on the face, point it away from windows, and keep the cable at least a metre from the cot. The long version is in where to put a baby monitor.

The feature landscape

This is where apps actually diverge. Here is what each feature is for, and which ones I would leave switched off.

Video and audio

Most nights the monitor is a speaker on your bedside table and you are listening rather than watching. The picture gets checked two or three times: when a noise is ambiguous, when you want to know whether the blanket has been kicked off, and when you want to see whether they have actually fallen asleep before you commit to sitting down. Get the audio path right first, meaning placement and distance from any white-noise machine, and the video will look after itself.

Cry detection

This is the feature that genuinely changes how a monitor gets used. Instead of leaving a live audio stream running all night and half-hearing it, you get a push notification when your child cries and can otherwise leave the phone alone.

How it is implemented matters. MonitorUltra classifies audio on the baby unit itself, using Apple's SoundAnalysis framework, the same on-device audio classification Apple ships in iOS. The sound is analysed on the phone in the nursery and is never uploaded for a server to listen to. That is an architectural difference from monitors that send audio to a cloud model, and how AI cry detection actually works goes through it in detail.

Set expectations honestly. A cry detector is a classifier. It is very good at telling crying apart from a quiet room, it will occasionally fire on a similar noise, and no detector should be treated as a substitute for checking on your child.

Motion detection

Camera-based, and the feature most likely to make you distrust your monitor. A fan, a mobile, a curtain near a draught or headlights sweeping the ceiling will all set it off. Being woken at 2am by a rotating fan blade three nights running is how people end up muting alerts entirely, which leaves them worse off than if they had never enabled it. Turn it off if the room contains anything that moves. When to use motion detection and when to turn it off covers the cases where it earns its place, mostly toddlers who climb.

Alerts that arrive when the app is closed

The test of a monitor app is whether it still works once you have locked your phone and put it face-down. Push notifications reach the parent unit with the app in the background or fully closed. There is also a Live Activity, so an active session stays visible on the Lock Screen and in the Dynamic Island instead of vanishing into a background task you have to take on faith. Being able to glance at the phone and confirm the session is running is worth more than it sounds in a feature list.

Sounds through the monitor

White noise and lullabies play through the baby unit's speaker, so restarting a sound machine no longer means walking into the room. It is a secondary feature, covered in white noise and lullabies through the monitor.

More than one parent

Several parent devices can watch the same baby unit at once, and each one receives its own notifications. This matters more than it looks on a feature list. A monitor that only one person can hold makes one parent responsible for every night. Both parents, one baby monitor covers what each device can and cannot do.

The network question

A lot of DIY monitor guides tell you both phones must sit on the same Wi-Fi network. Some apps do work that way. The phones themselves impose no such requirement, and the assumption quietly shrinks what a monitor is for.

MonitorUltra streams over Wi-Fi and over cellular. The baby unit sits on your home Wi-Fi, plugged in beside the cot. The parent unit can be in the garden, at a neighbour's house or in the restaurant on the ground floor of the building. Wi-Fi gives the lowest latency, so use it where you have it. There is no radio range to run out of.

Using a baby monitor over cellular explains what each end actually needs, and what to watch for on a capped data plan.

What happens to the video

Worth being blunt about, because it is the one decision you cannot undo later.

Many camera products upload footage so it can be played back, shared with grandparents, or run through a model. That is a genuine feature. It also means a database somewhere with your child's bedroom in it.

MonitorUltra does not record. Video and audio are encrypted in transit and relayed live to the parent unit through LiveKit. There is no recording on a server, no clip history and no stored footage, so there is nothing of yours sitting in a database to be exposed in somebody else's breach. I have written the architecture out in full, including the parts that are not peer-to-peer, in a private baby monitor that records nothing.

App versus a dedicated monitor

The honest comparison, because credibility is the only thing that makes the rest of this guide worth reading.

	Phone app	Dedicated monitor
Camera and microphone	Better, usually by a wide margin	Adequate
Range	Anywhere with signal	The radio's range, or your Wi-Fi's
Cost	Subscription, on hardware you already own	£80 to £300 up front
Distraction	The parent unit is also a phone	Cannot receive a phone call
Dependency	Your internet connection	RF models need no internet at all
Health sensing	None	Some models track breathing or SpO2
Lifespan	Until the phone stops getting iOS updates	Until the plastic breaks

Three things a dedicated monitor genuinely does better:

It is a single-purpose object. A parent unit that cannot show you a work email at 1am is a real advantage. If that appeals, use an old iPad in a stand as the parent unit and leave your phone downstairs. Using an iPad as a baby monitor covers that setup.
Some RF models need no internet at all. If your home connection is genuinely unreliable, a non-Wi-Fi monitor sidesteps the problem. Wi-Fi monitors from hardware brands have exactly the same dependency an app does.
A few do health sensing. Breathing and oxygen tracking sit outside what a camera app does, and no app should imply otherwise.

The full version of this argument, including which families should simply buy hardware, is in baby monitor app vs dedicated monitor.

Who this suits

It suits you if you already own a spare iPhone or iPad on iOS 17, your home internet is reliable, and you want alerts that follow you around instead of tethering you to one floor of one building. It suits travelling families particularly well, because the monitor is already in the bag. A baby monitor that travels with you covers that case.

It suits you less if the only spare device in the house is an iPhone 8 or an Android phone, if you specifically want breathing or heart-rate tracking, or if you need something that keeps working through a broadband outage.

The battery rule

The baby unit stays plugged in, permanently. A phone streaming video continuously will flatten its battery in a few hours and get warm doing it, so plan its position around a socket you can leave it in and treat it as a fixed appliance that happens to be a phone. The parent unit is only receiving, so it uses very little power and will comfortably last the night.

What it costs

The free tier is audio listening with basic noise alerts. That is a usable monitor on its own, and if audio is all you want, it costs nothing.

Premium adds video, cry detection, motion alerts, the sound library, family sharing and the Live Activity. On the web it is $7.99 a month or $49.99 a year, with a 30-day money-back guarantee, and it cancels any time. One subscription covers the family rather than each device.

What sits behind the paywall and what does not is set out plainly in what you actually get for free.

Frequently asked questions

Does it work on Android? No. MonitorUltra is iOS only, on both ends. There is no Android app and no web viewer, which is worth knowing before you plan around a partner's phone.

Do both devices need to be on the same Wi-Fi? No. The parent unit works over cellular. Wi-Fi is lower latency where you have it, and the two devices do not need to share a network.

Can I use a phone with a cracked screen? Yes, as the baby unit. Once it is paired and mounted you never look at its screen.

Is anything recorded? No. There is no clip history and nothing stored on a server. Audio and video are relayed live and encrypted in transit.

Will alerts reach me if the app is closed? Yes. Push notifications arrive with the app in the background or closed, and the Live Activity keeps the session visible on the Lock Screen.

iPhone baby monitor app: the complete guide