demtears wrote:Dave.
I was thinking about the same thing, I came across in a local bicycle shop an odometer with a remote pickup that attaches to the wheel and the receiver or counter could be installed on the inside of the camper. I dont know how accurate this would be and if it would count hiway speed I haven't researched into yet but I would like to know distanced the tear traveled and to incorporate it into my build.
JUST A THOUGHT!

Being a cyclist, I am familiar with cyclo computers. They use a magnet attached to a wheel spoke, usually on a front wheel. A pickup is mounted to the frame. The computer work counting the number of times the magnet passes the pickup.
Cyclo computers need to be calibrated for your wheel circumferance. I figure this by marking a line on the wheel and rolling it along a measuring tape. You'll need to make sure the computer supports your wheel diameter including the tire. If you can find one that supports your wheel diameter, I don't see any reason why they wouldn't work on a tear drop.
Installation may be tricky. You'll have to do some fabrication to adapt it to your teer. The magnet needs to pass very close to the pickup for it to work. And, the pickup wires are very fragile. I use wireless cyclocomputers on my bikes to avoid that problem.
Besides acting as an odomoter, they can tell you trip distance, average speed, total trip time, etc. They start at around $20. You can get them at any bike shop or online at
Bike Nashbar