I bought one of these units from heli-world. It's a "Radio Glove". It works well - it's nicely made as well. Keeps my hands nice and warm so long as the temperature is above 40 degrees or so (particularly since they are out of the wind). In freezing weather my hands still get chilly. Takes a bit of getting used to - but it's not too cumbersome.

I bought some of those disposable heat packs (you know - you tear them open and they stay warm for a few hours). I'm going to try one of them inside the Radio Glove next time it's real cold at the flying field.

Moses