There's a lot of cool radio-related things our smartphones could do but probably never will for regulatory/political/commercial reasons like you note.

My pet idea is to make some use of longwave! You know those time signals broadcast around 60 kHz? They cover thousands of kilometres from one transmitter. At 60 kHz the wavelength is 5 kilometres long and the RF tends to diffract around objects like mountains, buildings, etc. that get in the way. Longwave tends to penetrate underground, and through Faraday cages meant for short wavelengths.

Those time signals broadcast, in effect, 1 bit per second. The receiver is dead simple electronically and requires almost no energy to run. What if we broadcast a more modern error-corrected data stream? Every device could be supplied with a receive-only stream of a few hundred bits a second of whatever. I admit it's a solution somewhat in search of a problem. Weather updates? Emergency alerts?