If you have a phone with a headphone jack, you have a portable radio... without the antenna. But just plug in headphones and you're good to go.

Calling other phones.

USB OTG on android phones is severely underrated.

• I can plug in a USB drive and transfer files around, I've used this to manage my retro handheld SD cards before.
• You can tether your hotspot over Ethernet to your computer with an Ethernet adapter.
• You can plug Ethernet into your phone to get faster connections.
• You can plug a mouse into your phone and get a cursor on screen. Not super useful tbh, but kinda cool.
• You can use your phone as an external webcam for your computer.
• It's a bit more annoying than it used to be but you can use your phone as a universal IR remote with a small adapter and free apps (I miss my built in IR blaster from my S3).
• I haven't used it much, but I can plug in a RTL-SDR dongle and get aerial TV on my phone, or a radio spectrum analyzer. I used it to discover that my garage remote is about to die and that's why my car's garage button won't learn the signal.
• USB (or Bluetooth) game controllers just work.

Definitely a relatively niche usecase but I have SSH clients, terminal apps, RDP remote access clients, and other networking tools as apps on my phone for quickly messing with things. Very helpful to not need to bring out the PC when I'm fixing my network.

The ability to VPN into my home network to access my NAS. Honestly being able to access my NAS in general is already great for backups or just so I don't have to think about what's physically on my phone.

With a cheap Bluetooth device I can connect to my car's diagnostic port (ODBII) and check engine codes. No more trips to the mechanic just to get it diagnosed.

WiFi direct cameras are a great addon too. I have a wifi endoscope (camera on a long bendy stick) for inspecting inside walls and my phone works as a screen for it.

I got a waterproof case, so I use mine as a coaster.

I've been getting into having a pdf of the various manuals for things around the house on my phone. I recently consulted the manuals for my fridge, a new dehumidifier and the lawn mower and it was pretty awesome not having to find and dig out a paper booklet each time. My phone is on me all the time plus I can get rid of the paper copies.

Haven't needed it in a while, but a wifi analyzer to identify which band(s) are least crowded

I moved my PC to a corner of my house without an Ethernet jack, I didn't want to drill any holes, pull any cables, dug out an old smartphone, connected with a micro USB (!) cable, enabled USB tethering, connected the phone via WiFi and had a nice Internet connection

Fdroid, you scroll through it and find games and tools you didn't know you needed until you're either: in the middle of nowhere, or need a tool that you don't have and just use an app for.

I run a real linux on my phone, so I can use it for anything I can use my laptop/desktop/unix for. I think what people forget is that phones are ultimately just computers with a WWAN radio, and the restrictive nature of Android and especially iOS obfuscate that.

I use a Galaxy Ultra. currently an S22u previously a Note 9.

I use the stylus everyday. I tired a phone.sans atykus (Pixel Pro) for a month and got rid of it. The sylus is so handy

I have gone ----> Note 8, Note 9, S22u.

I draw work sketches all the time eg just this morning my parter sent me a photo of her mother's toilet and asked me how to fix it. I typed a long set of instructions, she said huh... And can you draw me a sketch, stylus out and I did and she said now she understands and fixed it herself.

Someone givea me some info, stylus out, tap the screen and start writing eg phone number, address etc. No unlocking necessary. I have used the stylus as a camera remote on the phone but not often.

The styus makes the phone so useful it still beguiles me how peoplendo without. I use a phone and desktop.

Syncthing

An excuse not to interact with people.
"Sorry, my notifications were off while I was busy yesterday and didn't have a chance to check it".

You can use it as a webcam if you suddenly need to work from home and there's a shortage of webcams.

Originally I had to install an app for that, but it shows up as a standard USB option on my Pixel now.

I recently used my phone to wirelessly charge someone else's phone that was about to die. Pretty useful feature in the moment. I only used that feature only that one time in the 2 years I've had the phone but it's nice to know that is an option.

My other half has new Ultra, I have an older Ultra model. Stuff i find invaluable that she hasn't used once:

• S Pen
• Modes & Routines
• Secure folder
• DeX (to a lesser degree than the above)

I try to use my phone as a Swiss army knife. Stuff I rely on that most normal users likely dont realise their phone can do:

• Using Kodi the phone becomes fully fledged mobile media player. Great for vacations in case of poor weather (in conjunction with HDMI lead, controller/wireless keyboard)
• OsmAnd navigation has an offline Wikipedia plugin. I set up a shortcut in it so i can display/hide all wiki entries nearby. Brilliant when on vacation
• All my main apps will work offline in case of data outage: navigation, notes, password manager, books, music, podcasts, media etc etc
• Password manager has more uses than simply handling passwords
• Playing video sites in the background ...with a timer if desired
• Browser with uBlock "etc"
• Manipulation of .pdf files
• A good launcher. Mine is always set up the same regardless of device - I can access any app within 2 swipes & 2 taps
• A good car dock
• Most don't realise that a simple DNS entry can help reduce the amount of ads they see
• All manner of nerdy tech shit to interact with stuff on my network. No normal human needs to know that this usage factor exists

And most importantly ...using the camera in landscape so images/video can be viewed properly on a TV or monitor. And not using digital zoom in the dark to record an entire concert from row Q

You can use most modern phones as a spirit level with the right app! It's really useful when doing projects around the house, not having to run around to find a real one. Quite accurate, too!

It's probably a tie between wikipedia and flashlight.

I used my phone a lot to stream games from my PC to other rooms. Connect a Gamepad and Hdmi cable, and you can play all games from your library. Lag is minimal, but I haven't tried it for competitive games.

What custom keyboard do you use, and which layout?

I use my smartphone to keep my book open when reading at a table. It does a pretty good job there.

Don't limit yourself to technical uses.

SSH

I recently started to use my phone to monitor the conditions of my plant collection with a couple of Sensorpush devices. They report temperature, humidity, barometric pressure, and vapor pressure once a minute via Bluetooth, and I get a notification if conditions deviate from what I set. It has been very helpful at dialing in things in and responding to problems.

I can do full fledged software development complete with fully desktop-equivalent Neovim on my phone.

That said, it's really not a pleasant experience. The CPU in my phone is pretty fast all things considered, but it still takes several times longer to compile a project than my laptop does; having this little screen real estate sucks; and since Termux doesn't enable predictive text on the onscreen keyboard (and predictive text is worse than useless when writing code anyway), the best I can hope for productivity wise is a keyboard like Hacker's Keyboard or Unexpected Keyboard that at least has functions like Esc built in. When I have a Bluetooth keyboard, I'm about half as productive as I am on a laptop. When I don't, writing the same program takes ten times as long. But it does have all the same features my desktop setup does, and it is usable in a pinch.

My favorite use for my phone was wabbitemu, which was a perfect emulator for the ti86 calculator I've used almost daily since 1998. Apparently my new phone uses a new architecture and the app doesn't work, so that's rather disappointing.

Plugging headphones into a jack port and taking the back of to replace battery.

As a VPN client, I dont mean for a connection to a VPN service to annoamyse my traffic, but for my own self hosted VPN so I can call home and access stuff on my network. Comes in handy for stuff like my password manager where I dont like the idea of exposing it to the internet but still need access when im out and about.

I use mine with Microsoft Lens (I know, but one of their best products that doesn't spy on you) as a document scanner and then sync it to my document server paperless-ngx.

It can angle correct, color correct, and has good filters for b&w and greyscale that often make it look like a real document scanner if your phone has a decent camera.

Much better than drive or any of the open source options to be honest, sadly....

Installing postmarketOS on it to turn it into a full fledged pocket PC. It now runs all your favorite Linux-compatible desktop applications except for those that don't have ARM64 versions, and even then emulation layers can fix this. It's not 100% as I haven't been able to get Steam working (it starts but errors out before the login screen) though I have seen some people have success on other distros so maybe it's a pmOS/Alpine/musl specific issue even though I was using distrobox with Debian to actually run it.