BioForce HRV (Heart Rate Variability), Smart Training System for Training Optimization, Includes Heart Monitor Bioforce HRV System includes, compatible heart rate monitor, HRV training guide, and integrated web app that lets you track your workouts, chart your progress, and join the BioForce HRV community Compatible with all bluetooth iOS and Android devices Optimize your training: BioForce will let you know the days you're at your best and ready to train to the max. It will also let you know the days you're not and need to rest. Provides a quick, easy, and totally non-invasive measure of readiness and fatigue. All in just 3 minutes a day. Used by professional athletes