How to use an old iPhone as a baby monitor

A spare iPhone or iPad can become the camera for a baby monitor if it supports iOS or iPadOS 17 or later and is in good condition. You also need a second compatible device, internet access and a subscription for a new MonitorUltra installation. Check those requirements before buying a stand or planning to use it overnight.

I build MonitorUltra. This guide covers preparing a spare device, pairing and checking it in the room where you will use it. For feature and cost comparisons, start with the iPhone baby monitor overview.

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 or iPadOS 17 or later. Check the installed version in Settings.
• Use an undamaged baby unit with a working screen, camera and microphone. Wi-Fi can provide internet access without a SIM.
• Use a suitable charger and a stable mount, with all cables out of the child’s reach.
• New installations require an active subscription; check any trial eligibility in the App Store.

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 details can be remembered for another session. Confirm the connection, moving image and sound each time you start monitoring.

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. The US Consumer Product Safety Commission recommends keeping monitors and cords at least three feet away. Use at least one metre in practice and reassess as your child becomes more mobile.
• 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 enabled, cry alerts can reach the parent phone while it is locked or the app is in the background. Permissions, Focus settings, connectivity and iOS can affect delivery. Classification may miss a sound or confuse another sound with crying.

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

Continuous capture uses power and can warm the device. Keep the baby unit powered during monitoring with a suitable charger and ventilation. Stop using a damaged or overheating device.

Check the parent battery too. Consumption depends on the screen, video, signal and battery condition. There is no measured battery-life figure in this guide.

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 can relay the stream between different networks. Both devices need working internet. Test the actual Wi-Fi or cellular connection and check your data allowance. Stay close enough to check on your child directly; an internet connection does not establish a suitable supervision distance.

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 no library of media recordings. This does not remove account, device or live-session security risks. Protect pairing details and keep your devices updated.

Does it actually replace a dedicated monitor?

It depends on the equipment you already have and the connection in your home. A dedicated radio monitor may provide monitoring without internet and a separate parent screen. A model with infrared night vision may also suit a dark room better. An iPhone camera requires available light; check the evening image before relying on the setup.

Reusing an available phone can avoid buying a camera. You still need a stand, power and subscription access. New web subscriptions cost $7.99/month or $49.99/year, with a 30-day money-back guarantee; App Store offers may differ. Compare the full cost over your intended period of use. MonitorUltra does not replace adult supervision.

Check the first session and an interruption

Keep an adult with the child throughout the test. Leave the baby app open, place an object in view and confirm that its movement and sound reach the parent room. Repeat with the lighting and background noise you normally have in the evening.

Lock the parent phone and check enabled alerts. If a notification does not arrive, inspect permissions, Focus settings, detection settings and both internet connections. A fan or sound machine can change what the microphone classifies. An absent alert does not confirm that everything is fine.

During a supervised test, briefly disconnect one device. Note what the parent screen reports, restore the connection and confirm that sound and moving video return. The app attempts to reconnect, but a frozen image is not a successful recovery. Repeat on cellular if you plan to use it. Use the checklist below to repeat these checks before each session.

Which device can you lock or use for something else?

Keep MonitorUltra open on the baby iPhone while it supplies video. Locking that phone, taking a call or opening another app can interrupt camera capture. The baby unit keeps the screen awake during publishing; lowering screen brightness is different from locking it. Apple's camera interruption documentation explains the background-camera restriction.

The parent device has a different job. MonitorUltra pauses its video subscription when the parent app is no longer active. Reopen the monitoring screen to check the moving picture. Background audio and notifications have their own settings and operating-system limits; test them on the parent device you will actually use. A Lock Screen activity is a status display, not a second live-video screen.

If a call or connection change interrupts a session, check the live image and sound again after returning to the app. Do not assume that a remembered pairing or an old frame proves that monitoring has resumed. The interactive checklist keeps these checks together for each session.

Frequently asked questions

Can I use an iPhone with a cracked screen? Use an undamaged iPhone or iPad running iOS or iPadOS 17 or later, with a working screen, camera and microphone. Check the device and charger before use. A SIM is unnecessary when the device has working Wi-Fi.

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? Keep the baby app open for video. The parent phone can receive enabled notifications in the background, subject to permissions, Focus settings, network and iOS behaviour. Reopen the parent app to check the live feed.

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