MurmeliAn old phone as a baby monitor: what it takes
Almost every household has a smartphone in a drawer that nobody uses any more. It still works, but the battery no longer lasts a day, and selling it is not worth the trouble. As a baby monitor, a phone like that can earn a second life – provided a few things line up.
This guide comes from the team behind the baby monitor app Murmeli. It describes what applies to any app of this kind, and it names the cases where an old phone is the worse choice.
What the old device actually needs
Three things decide it, and processing power is not one of them:
A working camera and microphone. The microphone matters more than the camera. Sound is what you actually react to at night.
An operating system the app still supports. This is the most common obstacle. Older Android versions and old iOS releases eventually drop out of support. Every app lists its minimum version in the store, usually far down among the technical details. Check it before you set anything up.
A charging cable and a socket within reach. More on that below.
What barely matters: storage space, camera resolution and processor speed. A baby monitor app transmits a picture, it does not process one.
Why a weak battery hardly matters
That sounds contradictory, but it is the practical heart of the matter: the device next to your child is plugged in all night anyway. A battery that only holds an hour is enough for that.
Video costs noticeably more energy than sound alone. An old device that charges and films at the same time gets warm. That is normal, but it means two things: the phone must not be covered, and it does not belong under a blanket or a cushion.
If your device has to work without a cable, switch the camera off and leave only the audio running. Plenty of nights get by without a picture.
Where the device belongs in the room
This is the part that instructions like to skip.
A charging phone has a cable, and a cable in a cot is dangerous. The device belongs outside the cot, out of the child's reach, with the cable routed so that it cannot hang into the bed. A shelf, a chest of drawers or a wall mount beside the cot are good places – not the railing, not the edge of the bed.
For the viewing angle a simple clamp mount or a heavy stand is usually enough. Make sure the arrangement cannot tip over.
What an old phone no longer does well
Three honest limitations:
Security updates. A device that no longer receives updates no longer closes known holes. For a phone that sits in a child's room with the camera and microphone switched on, that is worth knowing. If you use the device only as a baby monitor, install nothing else on it and sign in to nothing, the risk stays small – it does not become zero.
Low-light images. Older cameras produce more noise in the dark. Some apps offer a night mode that brightens the picture; that is not a substitute for the true infrared image of a dedicated night-vision monitor.
Screen burn-in. On OLED displays a permanently static image can leave traces. If the app can dim the screen or switch it off entirely, use that. It saves battery and heat as well.
At home and away
If both devices are on the same Wi-Fi, most apps connect them directly to each other. That is the fastest and most economical case.
When you are not at home you need an app that keeps working over mobile data – and by no means all of them do. With some, access from outside costs extra, either as a subscription or as a separate purchase. That rarely appears on the sales page and often only in the reviews. If it matters to you, check before you buy. We collected the pricing models of 28 apps: baby monitor app without a subscription.
Murmeli transmits in both cases: directly between the devices on your own Wi-Fi, over mobile data when the two are on different networks. Access from outside costs nothing extra – the app is unlocked once for CHF 4.90 and runs on Android and iPhone in any combination.
Keep an eye on your data allowance. Video over mobile data uses many times what plain audio costs. How much exactly depends on resolution and duration; your phone shows the real figure in the settings under "Mobile data" or "Data usage" – look there after the first night rather than guessing.
What else you need
The list is short:
- A power adapter and a cable long enough to reach
- A mount or a stable surface
- Both devices in airplane mode? No – the baby device needs Wi-Fi or mobile data
The old phone only needs a SIM card if it is to transmit over mobile data. On your home Wi-Fi it works without one.
When a dedicated baby monitor is the better choice
Two cases where hardware wins:
No network. A radio baby monitor works on its own frequency and needs neither Wi-Fi nor mobile coverage. In a holiday house without reception, or in a basement, that is the decisive difference.
Running without thinking about it. A baby monitor does exactly one thing and does it without an operating system, without notifications and without battery optimisation switching something off in the background. If you do not want to configure anything, you get there faster.
The reverse case argues for the app: you already have the second device, you do not need a limited radio range, and you want to hear your child even when you are not in the same building.
Whichever you choose: a baby monitor – app or device – does not replace supervision by an adult.
Frequently asked questions
Does the old phone need a SIM card?
Only if it is to transmit over mobile data. If the device stays on your home Wi-Fi, it works without a SIM card and without a contract.
Does an iPhone work together with an Android phone?
That depends on the app and it is the most common stumbling block. Several well-known baby monitor apps exist for only one of the two platforms – anyone wanting to combine an iPhone with an Android device falls out at that point. So check before you buy whether the app appears in both stores. If it appears in only one, no rating in the world helps. The best-known case is Dormi, which exists for Android only – we put the alternatives together here.
Does the baby device have to stay plugged in all night?
With video, yes. An old device will not last a night with the camera running, and a flat battery in the middle of the night is exactly what you do not want. With sound only, some devices last considerably longer.
Is an old phone in a child's room safe?
If it stands outside the cot and out of the child's reach, the charging cable does not hang into the bed and the device is not covered, the arrangement is unproblematic. The second point concerns the software: a device without security updates should do nothing besides run the baby monitor app.
How much data does the transmission use?
Plain audio uses little, video many times more. No reliable general figure exists, because it depends on resolution, frame rate and duration. Measure it yourself: after the first night the parent device shows you under "Mobile data" or "Data usage" how much the app actually consumed.
Can I use an old tablet instead of a phone?
Yes, provided it has a camera and a microphone and the app supports it. A tablet often stands more securely because of its size, but it also needs more room on the furniture.