Pulse rate measurement conveniently and accurately

convenient, just as accurate as the standard Brustgurtsensoren (Polar, Zephyr) one can determine the pulse rate during exercise. Works with popular apps like Runtastic or RunGPS very good. With pulse measurement of the battery lasts for about a day, with activity tracking with no pulse measurement more than a week. Too bad that the lithium battery can only charge ca 300x, that is, after the device is hazardous. Who uses the Pulsmeßfunktion rarely, which is with
Manage 300 charges for several years