Most parents already own the hardware for a very good baby monitor. The iPhone in the drawer with the cracked screen, or the iPad that got replaced two Christmases ago, has a better camera, a better microphone and a better screen than a £150 dedicated monitor. What it lacks is the software to behave like one.

This guide covers the whole setup: which devices work, where to put the camera, and the three things that go wrong most often.

What you need

Two devices. One sits in the child's room as the camera, called the baby unit. The other stays with you as the parent unit.

Both devices must run iOS 17 or later. That means an iPhone XS or newer, or an iPad from roughly 2018 onwards.
The baby unit does not need a working cellular plan, a SIM card, or an unbroken screen. It needs a camera, a microphone and Wi-Fi.
A charging cable and a socket near the cot. This is not optional, for reasons covered below.
Something to hold the device at the right angle.

If you only own one device, a partner's phone works as the second unit. Family sharing means you don't need two subscriptions.

Step 1: install the app on both devices

Install MonitorUltra from the App Store on the baby unit and the parent unit. On first launch, pick a role. The device in the nursery becomes the baby unit, and the one you keep becomes the parent unit.

Step 2: pair them

The baby unit displays a QR code. Scan it with the parent unit. That is the entire pairing step. There is no account to create on the baby unit, no code to type, and nothing to configure on your router.

Pairing happens once. When you use the same two devices tomorrow night, they reconnect on their own.

Step 3: position the camera

The biggest quality difference comes from where you put the camera, not which app you use.

Aim for a view of the whole cot rather than a close-up of the face. You want to see whether your child has rolled, kicked off a blanket, or stood up. A tight face shot tells you very little once they move.
Mount above and to the side, looking down. A phone lying flat on a dresser gives you a view of the cot bars.
Keep the cable well out of reach. This matters more than anything else in this guide. Standard safe-sleep advice is to keep cords at least a metre from the cot, and it applies to a phone charger exactly as it applies to a monitor's power lead.
Avoid pointing at a window. Backlight turns the cot into a silhouette. Point away from the brightest part of the room.

A cheap gooseneck phone holder that clamps to a shelf costs a few pounds and solves the angle problem permanently. Do not clamp it to the cot itself.

Step 4: set up alerts before you need them

Test the alerts while you are both awake, in the room, with the app in the background.

MonitorUltra runs cry detection on the baby unit itself, using Apple's SoundAnalysis framework. The audio is classified on the device, and nothing is uploaded for a server to analyse. When crying is detected, the parent unit gets a push notification even if the app is closed and the phone is locked.

Motion detection works from the camera. If there is a fan, a mobile, or a curtain moving in the room, turn motion detection off. Otherwise you will be woken by a rotating fan blade at 2am, and after a week of that you will stop trusting the alerts entirely. Cry detection on its own is usually enough.

Once the setup is finished, run through the old-iPhone baby monitor checklist before the first night. It covers the Focus modes, power and signal checks that catch people out after everything already looks like it is working.

The three mistakes people make

Letting the baby unit run on battery

A device streaming video continuously will flatten its battery in a few hours, and it will get warm doing it. The baby unit should stay plugged in permanently. Treat it as a fixed appliance that happens to be a phone.

The parent unit uses very little power, because it is only receiving.

Assuming it only works on your home Wi-Fi

A lot of DIY monitor guides tell you to keep both devices on the same network. That is a limitation of the app being used, not of the phones.

MonitorUltra streams over Wi-Fi and over cellular, so the parent unit can be in the garden, at a neighbour's house, or in the cafe on the corner. Wi-Fi gives the lowest latency, so use it when you can, but you are not confined to one network.

Not checking what happens to the video

This one is worth being blunt about, because you cannot undo it later.

Many camera products upload footage to a server so it can be played back, shared, or analysed. MonitorUltra does no recording at all. Video and audio are encrypted in transit and relayed live to the parent unit. There is no recording on a server, no clip history, and nothing that could be exposed in a breach of somebody else's database. What you never store cannot leak.

Does it actually replace a dedicated monitor?

For most families, yes, with two honest caveats.

A dedicated monitor has one real advantage: it is a single-purpose device that cannot receive a phone call. If you want the parent unit to be a screen that does nothing else, an old iPad in a stand does that job well.

A phone-based monitor also depends on your home Wi-Fi. If your router is unreliable, fix that first, whichever monitor you buy. Modern Wi-Fi monitors have the same dependency.

What you get in exchange is a far better camera, a real screen, alerts that reach you anywhere, and no second gadget to store when your child outgrows it.

Frequently asked questions

Can I use an iPhone with a cracked screen? Yes, as the baby unit. It only needs a working camera and microphone, since you never look at its screen once it is set up.

Do both parents get alerts? Yes. Several parent devices can watch the same baby unit at once, and each one receives its own notifications.

Does it work if the app is closed? Push notifications reach you with the app in the background or closed. There is also a Live Activity on the Lock Screen and Dynamic Island so the session stays visible.

What about an Android phone as the camera? Not currently. MonitorUltra runs on iOS only, on both ends.

How to use an old iPhone as a baby monitor