A smartwatch is a touchscreen wearable computer in the form of a wristwatch. While early models could perform basic tasks, such as calculations, digital time telling, translations, and game-playing, smartwatches have more general functionality closer to smartphones, including mobile apps, a mobile operating system and Bluetooth connectivity. Some smartwatches function as portable media players, with FM radio and playback of digital audio and video files via a Bluetooth or USB headset. Some models, called 'watch phones' (or vice versa), have complete functionality of a typical smartphone
While internal hardware varies, most have an electronic visual display, either backlit LCD or OLED or Hologram. Some use transflective or electronic paper, to consume less power. Most have a rechargeable battery. Peripheral devices may include digital cameras, thermometers, accelerometers, pedometers, heart rate monitors, altimeters, barometers, compasses, GPS receivers, tiny speakers, and SD cards, which are recognized as storage devices by many other kinds of computers.