Here's a great new device for cyclists. Garmin has developed a cyclometer with GPS functionality. It keeps track of your location, speed, distance travelled, altitude and much more and stores that data for future download to your PC. Big advantages that I see are no wires to the bike wheel, no calibration and the storing of data in digital form.
Image by Garmin
Lots of other features that you can check out at Garmin's GPS Cyclometer