It's a real shame phones don't have something like this built in. I mean, we literally have satellite communication in every iPhone – or, depending on how you count, every LTE phone, period!
Technically, it seems like 90% of what's required is already there anyway, but due to commercial and political pressures, we'll probably never see it happen.
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?
For example, the German LF time signal, DCF77, dedicates some of its "spare bits" to broadcast civil protection and weather forecast information, the latter of which many simple LCD "home weather station" thermometers can receive and decode.
GNSS (navigation satellite systems like GPS or Galileo) are also an obvious candidate for this, given that essentially all phones already can receive their signals.
> My pet idea is to make some use of longwave! […] At 60 kHz the wavelength is 5 kilometres long …
Dim memory from my Ham Radio days that you’d need an antenna length of 1/4 the wavelength, which wouldn’t be very convenient for portable devices, unfortunately.
Only for most efficient transmission. Reception just scales with antenna size, so as long as your transmitter is powerful enough in terms of effectively radiated power, you can make the receiver arbitrarily small.
Many wristwatches are capable of receiving these LF time beacons, despite usually having antennas more compact than several kilometers.
The 1/4 wavelength is derived from the half-wave dipole. It's not necessary to have an antenna that is 1/4 wavelength. It'll probably perform better if it is closer to that size, but it isn't required.
Actually some have. At least I know that in Peru, operators were forced to offer such a thing in case of earthquake. I do now have details though, maybe was not simple as I was told.
There's an app called Rattlegram that will convert data into audio that you can then send over a walkie talkie.
I wish the hardware was included directly in the phone. It would be super useful for outdoor activities where there's no cell service and you often end up just out of yelling distance.
Not that I don't agree that push-to-talk is a cool tool, but good lord was it a scourge in public environments. People shouting into their phones, then the Nextel "boop-boop" followed by a loud static-y response while you sit on the bus wishing for an asteroid.
Technically, it seems like 90% of what's required is already there anyway, but due to commercial and political pressures, we'll probably never see it happen.