The Inner Balance Trainer is optimized to ensure accurate HRV and Coherence measurement. Medical grade photodetector 125hz sample rate - measures your heart rate 125 times a second Auto gain control capable of changing resolution of measurement in real time State of the art, ultra-low Bluetooth working at an output power range of 0.5 mW or less, which is significantly lower than mobile phones 80 hours of battery life, display of battery level in app and auto-shutoff Ergonomic shape for easy placement with a low profile, lightweight design USB charging cable included