Jonathan over at Sentient sent me this great Skido cartoon recently - good fun and if you do any kind of sport, you should check this application out. Running on both Smartphone and Pocket PC, the SportsDo range of products utilises GPS to provide realtime information whether you're skiing, cycling, running and more. This really is a killer app and I wrote an article about it a while back on windowsmobile.com as I use this on my mountain back to track my speed, calories, distance and compare with previous trips.
The UI is very intelligently designed for an application that will be used on the move and is very intuitive. Don't take my word for it, go check out their webiste and download an eval version!