I love the geocaching idea, may need to shop for some GPS gadgets. I was thinking walking or trail walking.
I can't find any links to it, but in my confirmation booklet for the Hilly 100, they say that HAM operators will be in sag vehicles and on stops to help with any communication needs. Maybe you could tie this into some of your local rides. Maybe you could contact the Hilly people to get more info.
"Being retired from Biking...isn't that kinda like being retired from recess?" Stephen Colbert asked of Lance Armstrong