Why is Mio SLICE more effective than other activity trackers?

SLICE is the first device to feature PAI (Personalized Activity Intelligence). PAI is a revolutionary new system that turns the only measurement that matters – your heart rate – into a single, personal score. PAI shows you how much activity you need to stay healthy. Since it is calculated over a rolling 7-day period, you can be more active on some days, and less on others. You can choose any activity that gets your heart rate up, no matter how many steps you take.