How to turn an old Android phone into a home security camera

A spare Android phone already has a camera, a microphone, Wi-Fi and a battery. The missing piece is software, and which software you pick decides where the video of your living room ends up.

Written by the developer of Homeye, one of the apps compared below. Where that matters, it is said plainly.

What you need

• The old phone. Anything from roughly Android 7 onwards still works with most apps. A cracked screen is fine. A dead battery is fine if you keep it plugged in.
• A charger and an outlet near where you want to watch. This is the real constraint on where the camera can go, more than Wi-Fi is.
• A second phone to watch from, and Wi-Fi that both can join.
• Something to prop it up. A cheap clamp mount costs a few dollars. A mug works. The angle matters more than the mount does.

The three approaches, and what each costs you

1. An app that streams through the vendor's cloud

This is the biggest category: AlfredCamera, AtHome Camera, and most of what you find by searching. You install the app on both phones, sign in with an account, and the camera phone uploads to the vendor's servers. The other phone watches from there.

What you get: it works from anywhere, including mobile data. Motion clips are stored for you. Setup is genuinely easy.

What it costs: an account, and a copy of your video leaving your house. The better ones encrypt in transit and say they don't look at it, and I have no reason to think they're lying. But the video does pass through a machine you don't control, and the free tiers are usually funded by ads or by upselling storage.

2. An app that keeps the video on your own network

Both phones stay on the same Wi-Fi and talk to each other directly. Nothing is uploaded. IP Webcam works this way: it turns the phone into an MJPEG/RTSP stream you open in a browser, VLC or a network video recorder. Homeye, which I wrote, works this way too, with the second phone as the viewer instead of a browser.

What you get: the video never leaves the building. Usually no account. Lower latency, because the path is a few metres instead of a round trip to a data centre.

What it costs: you can't check in from the office. That's not a bug anyone can patch away cheaply, it's the direct consequence of having no server in the middle. Remote access needs either a relay server or your own VPN / port forwarding.

3. Phone as an IP camera feeding a recorder you run

If you already run Home Assistant, Frigate, Blue Iris or a similar system, the phone becomes one more RTSP source. IP Webcam is the usual choice.

What you get: recording, retention, motion zones, integration with everything else you run.

What it costs: a machine that stays on, and an afternoon. This is the best answer if you're already the kind of person who has that machine.

How to decide in one question

Do you need to watch while you're away from home on mobile data?

If yes, you need a cloud app or your own VPN. There is no third option that is honest about itself.

If no — you want to hear the dog from the next room, keep an eye on the front door while you're in the garden, watch a sleeping pet from the sofa — then a local-only app gives you the same thing without the account and without the upload.

Setting it up, local-only

Using Homeye as the example, because it's the one I can describe exactly:

1. Install the app on both phones and put both on the same Wi-Fi.
2. On the old phone, choose Use as camera, allow the camera permission, and plug it in.
3. On your everyday phone, choose Use as viewer and scan the QR code shown on the old phone.
4. That's the pairing. From then on, opening the app connects.

The same shape applies to the other local apps: install, allow, pair or type in an address.

Making the old phone actually survive

This is the part the roundup articles skip, and it's where most of these projects quietly die after four days.

• Keep it plugged in. Streaming video is one of the heaviest things a phone can do. On battery you get hours, not days.
• Exempt the app from battery optimisation. Android will otherwise suspend it in the background. On stock Android this is Settings → Apps → the app → Battery → Unrestricted.
• Check your manufacturer's own killer. Xiaomi, Oppo, Vivo, Huawei, Samsung and others each add a second layer on top of Android's — autostart lists, "protected apps", aggressive memory cleaners. dontkillmyapp.com documents the exact path per brand. This single step is the difference between a camera that runs for weeks and one that stops overnight without telling you.
• Let it get rid of the screen. A screen running all night wastes power and generates heat for nobody's benefit. Apps that do this properly dim to black while keeping the camera running.
• Watch the heat. A charging phone that is also encoding video runs warm. Take the case off, don't put it in direct sun, and don't wedge it into a bookshelf with no air. Sustained heat is what kills the battery, and a swollen battery in an unattended phone is the one genuinely dangerous outcome here. If the back feels hot to hold, improve the airflow.
• Prefer 5 GHz Wi-Fi if the old phone supports it, and put it where the signal is good. Video over a weak link is where stutter comes from.

What to expect, honestly

• Night vision: no. A phone camera has no infrared illuminator. In a dark room you get a dark, noisy picture. A cheap lamp on a smart plug beats any software setting.
• Field of view: narrower than a dedicated camera. Expect to cover one doorway or one corner, not a whole room.
• Reliability: lower than a purpose-built camera, because Android is designed to stop background work and every vendor tunes that differently. The honest goal is "it runs for weeks and tells me when it stops", not "it never stops".
• Audio: usually good. Phone microphones are better than the ones in cheap cameras.

Common problems

It worked yesterday and today the viewer says offline. Nine times out of ten the ROM killed the app. Go back through the battery-optimisation and autostart settings above.

The picture froze but it still says connected. Some apps don't detect this, because neither the camera API nor the streaming stack reports "the picture stopped" — they only report errors. If your app shows a stale frame indefinitely, that's what's happening.

The viewer can't find the camera on the same Wi-Fi. Guest networks and "client isolation" on the router block devices from seeing each other. Put both phones on the main network.

Two phones, two different Wi-Fi bands. Usually fine, but some routers separate 2.4 and 5 GHz into isolated networks. If discovery fails, try both on the same band.

Is a used phone better than a $30 camera?

A cheap dedicated camera gives you infrared night vision, a wide lens, and a device designed to run unattended for years. A spare phone gives you better audio, a better sensor in daylight, no new hardware in the landfill, and — if you pick a local-only app — no account and no cloud.

If the camera is pointed at something you'd be uncomfortable seeing on someone else's server, that last part is the whole argument.

A note on the law and on people: recording audio and video of other people has rules that differ by country, and in many places recording conversations without consent is a criminal matter. Cameras pointed at shared hallways, neighbours' windows or staff areas are a different question from a camera pointed at your own dog. None of this is legal advice.