I stopped using my phone as a security camera and used it…

There are so many use cases for old phones.

When you upgrade your phone, it's easy to think that downloading an app like Alfred and taping your old one to the window and calling it home security is a good use of your previous device. But there are a load of issues that this can cause. It can lead to battery swelling as leaving a phone plugged in 24/7 in a sunny window isn't healthy for the components inside. You don't have any night vision as without IR LEDs, your phone is blind the moment the lights go out.

And of course, latency. Most camera apps have a 2–3 second delay that dedicated PoE or Wi-Fi cameras solved years ago. My old phone made a mediocre security camera at best, but it has a high-resolution screen, a decent DAC, and a fast processor, so I turned it into a dedicated home assistant dashboard. From energy tracking to turning off devices when not in use, Home Assistant helps improve my life by automating my smart home.

Utilizing your phone as an always-on home assistant dashboard can be a great use case for an old device instead of fumbling for your main phone to dim the lights or check the front door (where you've got a real camera set up). You have a permanent wall-mounted command center or a dashboard that sits on the coffee table and is always just an arm's length away. To set it up, you can use the Home Assistant companion app or browser-based dashboard apps like WallPanel or Fully Kiosk Browser.

These apps allow you to lock the phone into a kiosk mode, which leaves the screen on and the dashboard front and center at all times. The benefit of using an older phone is that it'll be faster than any Google Home Hub and gives you granular control of everything from Zigbee sensors to PC statistics. Implementing a Home Assistant dashboard gives you complete control of everything on a device that you otherwise would leave sitting at the back of a drawer or taped into a window to ultimately pose as a fire hazard.

An important factor to consider is ensuring that you prepare the hardware accordingly. Battery health is a major point of concern when you're using a phone like this. Leaving it always on, whether it's wall-mounted or left as a control panel on a desk or counter, can lead to major issues, particularly if it's always plugged in. I'd recommend using a smart plug with home assistant automation to keep the battery between 20% and 80%.

This will prevent the device from overheating and overcharging, and destroying the battery even further. Prior to setup, a good protocol is to de-bloat the device, too. You can use ADB (otherwise known as Android Debug Bridge) to strip out Google Play Services and unneeded bloat, which will make the device run cooler and faster, and in turn, lead to less risk of overheating or damaging itself. Alongside being a standard Home Assistant dashboard, you can also use an old phone like this for a range of other use cases.

It can be a dedicated hi-fi music streamer. You can connect your phone to your standard speakers and then use the phone as a bit perfect streamer by running it as a dedicated device. You bypass the Android system mixer, which re-samples audio, and feed high-res audio directly into your amp. And in turn, you also get a beautiful now playing display for your desk that doesn't drain your main phone's battery.

It can also be used as a PC hardware monitor, whether that's internal or external. You can use Remote System Monitor or Goya's System Dashboard and mount the PC inside your phone case or prop it under a monitor so that way it shows you real-time CPU and GPU temps, clock speeds, and FPS. It saves your main monitor's real estate and adds a futuristic aesthetic to your setup. While I would wholeheartedly recommend against mounting it inside your PC case unless you've got extremely phenomenal active cooling, it still makes a great addition to your setup outside of your case, too.

Another great use case for an old phone is a 3D printer controller. If you have an old Android phone with a decent camera, it can be a better brain for a 3D printer than a Raspberry Pi, which can still be hard to find or even just overpriced. Pick up Octa4a or OctaPrint, and then the phone handles the web interface, the G-Code streaming, and the time-lapse recording all at once. Plus the built-in battery acts as a mini UPS in case of a brief power flicker.

A phone is essentially a supercomputer in your pocket, and using it as a static camera can be a waste of its full potential. Whether it's a smart home remote, a Plex controller, or a dedicated hi-fi streamer, the best use for an old phone is something that utilizes its interactivity rather than just its lens. Even if none of these use cases specifically apply to you, there are a range of ways that you can use your old phone that are tailored to your needs and requirements.

Summary

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