The one in the drawer is not rubbish yet
A phone that is too slow for daily use is still a capable computer with a camera, a screen, a microphone and wifi. The reason to give it one job rather than several is security: it has stopped receiving updates, so the sensible arrangement is a device that holds nothing personal, does one thing on your own network, and can be wiped without anyone caring.
Before it does anything, clean it out
- Back up anything still on it Photographs and message history first. Everything after this step assumes the phone is expendable.
- Sign out, then factory reset Removing the account before the reset avoids the activation lock that otherwise makes the phone useless to you and to anyone else.
- Set it up with a throwaway account, not your own The second job does not need your mail, your photographs or your password manager anywhere near it.
- Install only what the job needs One app, updated, and nothing else. An unpatched phone with fifteen apps on it is a different proposition from one with a single camera app.
- Keep it on your own network, not exposed to the internet Almost every job below works over the local network. Forwarding a port to an unsupported phone is how these projects go wrong.
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The jobs, and what each one needs
Turns the phone into a home camera with motion alerts to your current phone. The easiest of these projects by a distance, and it needs an account and an internet connection.
The local alternative: the phone serves a video stream on your own network, with nothing leaving the house. More setup, far more control.
A dashcam with loop recording, so an old phone on a windscreen mount covers the job without buying hardware. Heat in a parked car is the practical limit.
A music player for local files with no account and no streaming, which suits a phone that lives in a kitchen or a workshop.
The heavier player, worth it when the phone is wired into real speakers and the equaliser matters.
Plays whatever else you put on it, including video and network shares, without a subscription or a login.
Internet radio, which is what most kitchen phones end up doing all day.
A bedside e-reader with the screen dimmed and the wifi off. An old phone is a better reader than most people expect.
Offline Wikipedia on a phone that never leaves the house, which makes a surprisingly good reference device for a child.
Clock, weather and calendar widgets, for a phone propped on a shelf as a permanent display.
Uses the phone as a small second monitor for a computer over wifi. Good for a chat window or a dashboard, not for anything that has to be sharp.
Locks the phone to a chosen set of apps, which is what makes an old handset usable as a child's device rather than a small unsupervised internet.
A bedside sleep tracker using the microphone and the accelerometer, on a phone that is plugged in permanently and not carrying your mail.
A baby monitor between two phones, which is exactly the job an obsolete handset is well suited to.
Offline sat nav for the car, on a phone with no SIM. Downloaded maps need no network at all, so an old handset does the job with nothing but power.
For the more involved version: a small always-on machine on your network running scripts. Battery and background limits are the real constraints, not speed.
The physical side people forget
| Job | What it really needs | The thing that goes wrong |
|---|---|---|
| Home camera | Permanent power and a mount | The battery swells if it is charged at 100 per cent for months |
| Dashcam | A windscreen mount and a car charger | Heat in a parked car, which kills batteries fast |
| Music player | A stand and a cable to the speakers | Bluetooth dropping out when the phone sleeps |
| Clock or dashboard | A charger and screen-on settings | Screen burn on an OLED panel showing a static clock |
| Child's device | A case and a locked-down launcher | Everything, if the app list is not restricted |
| Sat nav | A car mount, no SIM needed | Offline maps not actually downloaded before the trip |
Leaving a phone plugged in permanently is the shortest route to a swollen battery, and a swollen battery in a hot car is worth taking seriously. If a phone is going to live on a charger, a smart plug on a timer, or a charge limiter where the phone supports one, will extend its life considerably.
Reset it, sign in with an account that does not matter, give it one job on your own network, and watch what permanent charging does to the battery.
Frequently asked questions
Is it safe to use an old phone that no longer gets updates?
For a single job on your own network with no personal accounts on it, the risk is small and manageable. For anything holding mail, documents or money, no: unpatched is unpatched.
Can I use it without a SIM card?
Yes. Everything above works over wifi, and the offline maps and media players need no connection at all. It cannot call the emergency services reliably without a network, so do not rely on it for that.
What if the phone is too old to install anything?
Below roughly Android 8 most current apps refuse to install. At that point the useful options are the ones that need no app: a clock, a torch, a music player, or the parts recycling value.
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