Breezewood

Interesting, after following the link in your post, I did some research on those Garmin units and it appears that the Group Ride Radio feature you mentioned also includes data transfer of locations of other users. I imagine this to be a scaled down implementation of part of the idea behind APRS...

I have one of these and, sadly, the external shielding on the wiring is deteriorating quite badly... I wonder how difficult it would be to replace it all...