I should make a small, free cell phone using a Raspberry Pi Pico. It would have an oled display for viewing text. Ideally, it would have a 12 key mechanical keypad. It could also have a dial, similar to the dial on the apple watch. Since the Pi Pico isn't very powerful, it would have to be a pretty limited phone, the most advance thing it could do is maybe a text-only browser. Since the pico has Bluetooth and Wifi built in, the only wireless communications i'd have to figure out is cellular. If I can't get cell working, I could always use the wifi for VOIP. For text, I could use Matrix or IRC
This may seem like a lot for a Pico to handle, But the original Pico was powerful enough to emulate a Macintosh, so the second generation Pico shouldn't have too many problems with something as simple as displaynig text
The phone would likely be much thicker than most modern phones, but the device isnt meant to be used as a modern cell phone. I would license the code under the gpl.