Has anybody built something like this yet?
FPV pilots (like me) use analog A/V links of course, and one of the existing audio channels can be used for telemetry. Telemetry can be then decoded on the ground and the GPS coordinates can be used to aim an antenna tracker.
Using an audio modem chip to encode (parts of) Mavlink data and output it as analog audio for the A/V transmitter, will mean saving on a redundant, interfering, and range limiting external wireless modem set.
The audio modem will of course have to be more or less immune to noise, and transferred data will require error detection and correction code.
I wouldn't mind trying if I had the time, but it would be overwhelming as my 1st Arduino project ever, and I'm not even sure which components I would need. I don't even have an electronics background.