If you're into HomeAssistant, you can turn one into something akin to an Echo Show, complete with local voice assistant.

Just yesterday I learned the Echo Show 5 can be pwned so I dug mine out, put LineageOS on it, and now it's a satellite for my HA server. Her name is Janet now.

Put most of your apps on the spare phone, only put apps needed to leave the house on your primary phone. This helps with battery life, storage, and privacy.

I do:

    Secondary camera (with OpenCam) *oss

    Security camera (various software)

    Alarm clock with custom audio files (tibetan bells make a very unobtrusive wakeup sound)

    Guitar tuner & general audio                      recorder

    Mp3 player while working in harsh environments 

And it stays simless, in airplane mode, after a nice adb session where I uninstall just about everything I can. I could easily live without it, but I'm often glad to have it.

Are you plugging them in for permanent use? Or are you using them as mobile security cameras?

Around house. When in use, I piwer it with an old nook charger which I think is gentler on the battery.

I can always find a purpose for an old phone. But nothing on the Internet, unless it still gets updates.

You can turn one into a server.

I used to keep one as a sort of backup internet connection, since there are "unlimited 4 hours of internet" prepaid plans, like $1, here that work pretty well when used as an access point if your home internet's down for whatever reason.

Nowadays I just sell them

Boring answer. Your first case - testing for app development, web development, display variations, device feature variations.

A little bit of @hnburnsy's answer, with segmented logins and emails separated by phones with layered restoration so it's difficult to accidentally get bricked by having one system get malware, system faults, or other failures. Two-Factor Auth also gets separated around between devices.

I have a $180 spare Android phone. I slapped PagerDuty on it to serve as my on-call phone. I also installed WhatsApp and Signal on it as I don't want to keep them on my primary phone (less distract).

Since I opted out of Google via GrapheneOS, I use one of my old phones in my car just to navigate.

Another phone is an audiobook listening device for my kids (they choose and I play).

Of course I also have a dedicated dev phone.

Could be cool to use one as a speedometer or pedometer. But the accelerometers are probably not good enough.

I just want a LineageOS fork that is just some retro game emilator in proper kiosk mode or makes two phones work togther somehow as a big tablet or screen and keyboard combo

I always wondered if they'd be of any use as multimedia server, with local content deliver and an USB device hanging out of it, for unused libraries...

Suggestion: https://www.androidauthority.com/where-to-donate-old-cell-ph...

I use a non-smart, non-internet phone but I do have a android phone in the car to make the multimedia/maps/whatever work properly - more and more stuff assumes you have a modern spyware device

I don't know why you got downvoted so I could not reply your question. Here is my reply:

> Out of curiosity, have you found any downsides with that setup long-term? Battery health or missed notifications, for example?

Yeah, it is inconvenient to bring two phones. That's definitely a downside. Battery health is fine. I never missed any notifications so far.

Thanks for clarifying, that’s helpful. Battery health was exactly what I was curious about, since long-term standby usage can sometimes degrade older cells faster than active daily use. Good to hear notifications have been reliable so far. Have you noticed any differences over time in idle drain or thermal behavior when the device stays online continuously?

Mine is bricked forever because google non consensually entered me into 2fa using a dead email address. Which is good because I needed a reason to never trust those fuckers again.

Use it as storage lol

> I’ve been thinking about practical ways people reuse spare or unused Android devices instead of letting them sit in a drawer.

I sell them or give to family.

> Not trying to promote anything here — genuinely interested in how people approach this.

Adding this makes me think you do want to promote something.