Polar refers to its latest sports watch as a training computer, and it includes some features useful to athletes that you won't find on just any activity tracker. It monitors training and daily activity and then uses that data to calculate how long an athlete needs to rest between sessions. It can measure heart rate while swimming and has a built-in barometric pressure sensor, as well as continuous GPS tracking. The device can also send all its collected data to a smartphone, but it stores up to four weeks of training history in the watch itself. The device is expected to launch in April for $449.95.