This is the only personal, portable device available that measures your ground speed and distance while skiing, snowboarding, or sledding, providing a readout on a wrist unit so you can easily track total range and best speeds.

Ski Snowboard Techo Spedometer Portable Wrist Watch
The small, wireless, coded radio-frequency transmitter attaches to your boot, leg, or waist and projects a radar signal to measure average ground speed in MPH and KMH, as well as maximum speed, pace in minutes per mile, distance in miles, total distance, and elapsed time. All information is sent from the transmitter to the watch display, which has a built-in lap counter, alarm, backlight, stopwatch, calorie counter, 12/24 hour time, date, and three automatic speed modes (cross country, downhill, Nordic). Easy install ation takes two minutes. The low-profile transmitter will not interfere with your movement, and is weather-resistant to withstand winter conditions and can be worn under clothing.