Mio Vital Petite Heart Rate Watch (Black with Blue Accent) ECG accurate heart rate, without a chest strap; visual indicator of exertion level based on heart rate and personal data Percentage of maximum heart rate display based on age and gender Advanced ergonomic sensor technology Full-featured sports watch with date/time/calendar, alarm, chime, backlit display with 30-meter water resistance User accessible battery hatch; water resistant up to 30 meters