The Jawbone UP4 activity tracker is the wireless-payment-enabled sibling of the UP3. The connected fitness tracker brings all the good looks expected from Jawbone design. as well as a suite of activity and bio-metric monitoring sensors and features. The UP4 allows you to monitor idle time. active time. sleep quality. steps. and calories. Bio-impendance sensor allow you to monitor resting heart rate. respiration. and galvanic skin response. You cna link your UP4 to eligible American Express cards to enable NFC-powered wireless payments. Three single-color LED lights provide alerts to notifications. sleep. and activity. The UP4 fitness tracker is compatible with both iOS and Android smartphones.