what can an apple watch track?
<answer> An Apple Watch can track activities like swimming and it can measure the heart rate through an accelerometer. <context> The Apple Watch will track movement through a built-in accelerometer and heart rate through optical sensors in the back of the device. It will extrapolate further data from the GPS and WiFi on the user's iPhone, which (contrary to certain predictions) will be required to use many of the features of the device.