* * |
"
Maybe I'm wrong (it's happened before), but it's my understanding that
FLARM
only works with other FLARM-equipped aircraft. Maybe it was
originally that
way and has since been corrected, but, if my assumption is correct,
how
would it prevent a collision with an airliner?"

PowerFLARM as is being sold in the US and Canada certanly detects
other FLARM-equiped aircraft as in Europe and elsewhere. However
PowerFLARM also detects ADS-B, Mode-A and Mode-S equipped aircraft, so
can give a warning against impending doom from "regular" aircraft
traffic. You don't look at the thing unless it's screaming at you,
then it tells you at a glance which way to look for your traffic. Of
course you still need to be looking out the window for those people
who have mandated themselves off the grid...

Cheers,

Derek