PhyPhox app. Let's you access every physical sensor your android device SoC has access to (at least for most major manufacturers). Especially on high end phones, they include a huge array of sensors from accelerometers to magnetometers to high accuracy air pressure barometers. Plus it includes a lot of processed sensor outputs, like rudimentary range finding sonar, audio frequency spectrums, etc... And it's free!
I assume this is pretty basic for people on Lemmy, where you can't throw a rock without hitting a couple of programmers and Linux nerds, but I always feel so cool using Termux to SSH into my laptop that I use to self-host a couple of things. Makes me feel like a 1337hax0r person.
I like JustWatch because it lets you search all your streaming services at once. If you set up a (free) account, you can limit it to just the streaming services you have personally. Handy as hell.
I find it cumbersome to ensure they stay charged. I already have to manage that with my phone and this way I can use it whenever the occasion arises. It does feel nicer tactile-wise tho with a gameboy
I use the desktop mode of my phone when I want to multitask my laziness in multiple windows simultaneously. I can YouTube using vanced, scroll through Lemmy and read manga.
I've been playing around with Super Image more and more. Recently I used it to upscale some Ghibli stills so I could use them as wallpapers. It's so neat to me that I can do it all offline, with the power of my own device.
You can turn an old phone or laptop into a wifi extender.
You can use an old iPhone to get iMessage working on an android.
If you attach a lens to it you can use your phone as a binocular
You can use your phone to scan a document and turn it into a digital file.
You can use it to make a signature, upload to computer to make a legally binding e-signature (the security of this is ambiguous, do at your own risk).
Theres probably an app somewhere to use it as a trackpad (if not can somebody please do this).
I'm pretty sure there's an app to use it as a secondary monitor for your PC or laptop
If you ever repair or fix things, take pictures at various points to have a reference to how it comes back together.
It you ever need to remember anything just take a picture. (Use this all the time at work for stocking things, take a picture of its location address, walk down the warehouse etc)
I think there's an app to use it as an angle gauge by tilting it. Used for hanging pictures and stuff.
Probably a pair of calipers with the right app and calibration.
You can get a "remote controlled button presser and switch flicker". You attach it to a light switch or anything else to remotely activate it. Great for turning on and off a space heater or computer.
Use an old one as a remotely viewable security camera, with battery.
Pierce the battery to make a fire (can only be used once)
I... I do distro hopping with my phone (custom roms/open bootloader) I know there are huge ass communities for that, but at least I don't know anyone who bothers with this in person lol.
That comes with flashing modules and stuff, because no root, no fun.
I also play Dragon Ball Z Budokai Tenkaichi 4 (no bait), I am talking about a fan game made for PS2, I use Aethersx2 and I think I should be using Nether...
I manage my Synology NAS and docker stuff from here, apps like Androtrainer and nzb360 are good for this, aside the usual Synology utilities, also I control my Nvidia Shield TV with the official app... And talking about that I would never understand why people bother with apps such as "Downloader" I always find better easier and have more control when I download the apk or whatever I want to put in the Shield and share it form my phone through SMB (in this case X-Plore) or even from my MacBook Pro... I mean, I could take it for devices such as Chromecast with Google TV which don't have SMB by default...
I haven't done much with it yet but I have Termux installed on my phone. Termux is a free and open source app that, while it's very limited, allows you to run Linux applications on an android phone/tablet. So far the only things I've done with it was that I ran neofetch and I used ciso to compress some iso files into cso files, both of which were just to test it out and get used to using it. I do plan on enabling and trying out X11 at some point but android prevents Termux from having hardware acceleration and the amount of software available for non-android Linux distros is very minimal, so I have no idea how useful it would be.
I make music with Koala Sampler, a Samson Go mic, and an $8 DAC for line-in and headphones. It's no PC/DAW, but there's more versatility there than you'd expect. Especially if you consider I've also got Csound, Caustic, and Grainstorm for creating samples and other audio processing.
It's a surprisingly decent condenser. And it's got a headphone jack. Class compliant. I was using it with an older Linux laptop a while back, now with my phone. I'm getting more use out of it than I expected.