GPS + Cellular model lets you call, text, and get directions without your phone3 Measure your blood oxygen with a sensor and app1 Check your heart rhythm with the ECG app2 The Always-On Retina display is 2.5x brighter outdoors when your wrist is down S6 SiP is up to 20% faster than Series 5 5GHz Wi-Fi and U1 Ultra Wideband chip