With GPS, the hard part isn't figuring out where you are, it's telling the rest of the world where you are.

A lat/long position is about 50 bits. Talk about serious bandwidth...

Oceans are huge. Where do you send those 50 bits if you are 1000s of miles from anywhere?

Satellite. The so-called cost concerns are just stupid, if I can afford a satellite phone airlines can afford to report 50 bits to satellite every 30 seconds.

With a little bit of trickery you could even easily cut that by half (e.g. drop the first few significant digits because the general area you're flying through can be assumed to be known, etc.).

Eww. So now the entire system depends on database matches back at home to work at all (since positions are relative, not absolute) and you have to test and engineer it significantly more to look for possible problems caused by hacking it this way.

Just eww. That's a terrible idea. Just spend the extra bits and save the headache of over-engineering it and then trying to fix all the problems you'll inherently create.

Yeah, I know. But the point is, it's few dozen bits every other minute - airlines, come on, Iridium can't be that expensive.

Right.

And if they don't hear you or you don't hear them, any non-zero bandwidth is a non-contact.

The phone itself is not capable of receiving the aircraft broadcasts/transmissions as they are sent at very specific radio frequency. All of what you see is actually being aggregated by a remote server from a number of receivers across the world that are capable of reading such radio frequencies, and transmitted to your device simply using Internet/3G/Network over HTTP/HTTPS.

Certainly. However, if you are here https://www.google.com/maps/place/Mariana+Trench+National+Wi... how would you communicate that to the rest of the world? That is the harder part.