Hello Shelley, thanks for asking! This watch is intelligent enough to know when to turn itself on and off. You can also change these wake-up settings to fit your preferences. However, if certain silent modes are turned on, such as Goodnight mode, the screen may not wake up when you raise your wrist. This watch is also compatible with Samsung Smartphones, Non-Samsung Android Smartphones(Android OS 5.0 and above RAM 1.5GB and above), iOS 9.0 and above iPhone 5 and above. ^Elizabeth