I read some research awhile back from the NTSB, I believe, that reported less than half of the airplane crashes the transponders go off. If it wasn't mandatory I wouldn't have one in our 170B. I use a spot gen 1 attached to my parachute on the shoulder strap and looking at my traces it seldom misses a track, like once in several hundred tracks. Also Steve Fosset had two ELTs one was a wrist watch ELT that also failed.