It uses some cel phone frequencies, among other things.

IMO, it's just too simple a system for the FAA to ever consider
adopting.

Just think how cool it would be if all aircraft carried one:
Fewer collisions at uncontrolled airports.
Less need for Xponders on VFR aircraf flying near congested IFR type
airspace, we'd see the airliner coming - and they would see us.
Etc...

If FLARM can really not give too many false positives in gaggles, just
think how well it would work in the above situations.

-Tom