Based on the classic Karvonen (heart rate reserve, based on the difference of your heart rate with your rest heart rate, compared to your max heart rate minus your rest heart rate), this app displays the heart rate and the effort zone: 50-60%: Zone 1, "Walking", Moderate Activity (Maintenance / Warm-up / Recovery) 60-70%: Zone 2, "Jogging", Fat Burning (Long Distance / Fitness / Weight Control ) 70-80%: Zone 3, "Running", Aerobic (Cardio Training / Endurance) 80-90%: Zone 4, "Hard Running", Anaerobic (Hardcore Training, Resistance) 90-100%: Zone 5, "All out", Maximum Effort (VO2 Max, Interval Training). As a small twist, the app displays both the HR (before the dot) and the Zone (after the dot). It also beeps with a number of beeps corresponding to a zone when you enter it. There's a buffer to prevent it from beeping continuously when you are close to the boundary between zones. App derived (many thanks, guys) from: Training Zone: http://www.movescount.com/apps/app4056-Training_Zone...