The new smaller and lighter Suunto Foot POD wirelessly transmits speed and distance data to your Suunto t3, Suunto t4, or Suunto t6 heart rate monitor. When combined with the integrated altimeter of a Suunto t6, you'll get an even more complete picture of your performance - uphill, downhill, and on any terrain.

Lightweight (27 g/0.95 oz including battery)
Wireless transmission (up to 10 m/30 ft)
Water resistant to 30 m/100 ft
Disturbance-free ANT transmission technology
Operating temperature: -20°C to +60°C/5°F to 140°F
For outdoor AND indoor use
Speed measuring range: 1.5 - 5.5 m/s = 4.5 - 16.5 ft/s = 5.5 - 20 km/h = 3.4 - 12.4 mph
Speed limit alarms
Average speed
Lap distance and automatic lap times
User-replaceable battery

You can see Suunto T6 here