Summary: I bought this product to measure my walking distance. It worked reasonably well at first and seemed to be somewhat accurate, except on long distances. After about a month, it totally stopped working, even with new batteries. Amazon sent me a new one, but the calibration is off by a long shot.
Summary: I purchased this extra collar (Transmitter) in addition to the Garmin GPS and have used it to help keep track of an elderly hunter in our group. I put it around his leg and I could tell where he was at all times. It works perfectly! I'm very pleased with this product.