Wahoo Fitness Fisica Sensor Key for iPhone

Make your iPhone® into a heart rate monitor. This key fits into the 30-pin connector slot, and then wirelessly links to your fitness measuring devices, including heart rate sensors, speed and cadence sensors, foot pods or power meters.

• Compatible with iPhone 3G, 3GS, 4, 4S, iPod touch, and iPad.
• Works with Garmin and Timex sensors, plus those from many other manufacturers. For a full list of compatible ANT + units you can visit the vendor's website.
• Very low power usage.
• Sends and receives signals up to 3 metres (unobstructed).
• Free apps are available (and paid options) to display, save, analyze and inspire your workout.