The Garmin Tempe is a wireless temperature sensor. It uses the ANT+ wireless network to transmit to a number of Garmin devices including the Forerunner series, all of Garmin's GPS's, the Garmin Etrex series, and the Garmin Foretrex 701 Ballistic Edition.
The Garmin Tempe securely attaches to backpacks, shoes, and jackets, keeping a low profile as it does it's job. While you can attach it to the Foretrex 701 wristband, it's best to attach it to something nearby, so the temperature isn't affected by your body heat.
Don't leave in direct sun as it will alter the temperature reading.
The battery is a replaceable 3 volt CR2032. The Garmin Tempe has a long battery life of up to one year, and operates in temperatures from -4 degrees Fahrenheit to 140 degrees Fahrenheit. The Garmin Tempe is also water resistant to a depth of 32.9 feet.