5Z wrote:
It uses some cel phone frequencies, among other things.

FLARM would need to operate on a slightly different frequency in the US,
but the main reason it can't be used here is that the FLARM people are
scared of our liability laws, and their licensing agreement explicitly
prohibit use in the US or in aircraft carrying US citizens.

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

Tis true, but it is also too simple a system for the ICAO to adopt.

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...

That would be called "ADS-B" not "FLARM".

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

FLARM is just too simple to be useful with aircraft flying more than a
couple of hundred knots, nor does it integrate into the air traffic
control system. There are always tradeoffs...

Marc