If I understand FLARM correctly

For Flarm to be effective, the other guy has to have Flarm installed too?

"FLARM (the name being inspired from 'flight alarm') obtains its position from an internal GPS and a barometric sensor and then broadcasts this with forecast data about the future 3d flight track. Its receiver listens for other FLARM devices within typically 3-5 kilometres and processes the information received."

From the above I deduce that Flarm only works if the other guy has Flarm too.

I fly a rental 1-34 and Grob 103 with no radio, no audio vario and in an environment in which at times one can find several gliders in close proximity. I bought a portable Icom A24 radio (recommended) which is only good when the other guy has a radio and either listens to my reports or makes his own. I bought a wrist mounted audio vario so I could listen for lift as opposed to flying with my head in the cockpit (and up my a--) looking for a hopeful move from the vario needle. I bought a parachute when I found myself thermaling with others in close proximity, some of whom did not appear to be lookin' where they were goin'.

I doubt if the rental ships are going to find themselves Flarm equipped and It would appear that these are hard wired, hard installed types of devices. Portables don't appear to be part of the senario. Gee, maybe we need battery powered strobes on the top of the rudder to improve our visibility.

Walt