The K10 Sim Card Supported Smart Watch has a built-in SIM card slot, so you can insert a SIM card and use it as a standalone device. This means you can make and receive calls, send and receive text messages, and use data services without having to carry your phone with you. The K10 Sim Card Supported Smart Watch has a heart rate monitor that you can use to track your heart rate throughout the day. This can be helpful for monitoring your fitness and for getting an idea of how hard you are working out.