Find My Phone is a fairly popular Android app that helps you track your phone down. The Find My Phone smartwatch app extends the same functionality on your wrist. Since your smartwatch is constantly communicating with your phone, it makes use of that channel and keeps a track of your phone.
The interface is fairly simple and the color scheme as you can see is very flashy. This is a good app to have if you have invested in a smartwatch that runs on Android wear.