I talked to Mike at Tinyvette and got the info on the communications set up they use.
"Our radios are Midland GXT-1000's. They cost $80-90 a pair. We've got 8 now, enough for the whole crew plus extras. Lots of channels, so you won't have a problem finding a clear one at the races. Range is good, too.
These radios come with rechargeable batteries, but they also take AA's, or is it AAA's, which is nice in case you forget to recharge.
You can get the radios at REI.
The ear buds that come with the radios work fine but they are delicate.
One-by-one our guys are investing in the Sampson helmet kits. They work great and hooking them up is easy. Having the PTT button on the wheel is real nice. But ... $$. The LeMons forum has discussed lots of cheaper alternatives, but by the time you get all the hardware and assemble it, there might not be much savings going that route. Sampson also sells radio kits, so if you want to go with their headsets their kit price might be a deal.
Check out the Sampson site anyway. They offer other radios as well so that will give you an idea of what else works.
If going for the Sampson helmet kit, we use the IMSA style (4-conductor) connector, in case you want to be compatible with us. ;)
I also bring a pair of standard stereo headsets to races. Mine has a 1/8" phone plug that I can plug into the radio and it sounds fine. More comfortable than ear buds in the paddock, and since they block most paddock sounds you can hear better, and you don't have to pull your radio out of your pocket and ask the speaker to repeat what they said."