I bought mine for geocaching but I find it really handy when biking as an odometer, speedometer, compass, etc..
I also do some side work installing low voltage stuff and I use it to record my route to a job site the first time. Then when I go back later to finish the job and I find that I have misplaced the directions to the house, (I ALWAYS lose them!) I just recall the route and I am on my way.