Over the last 10 years I tried all kind of hard/soft combinations to map my running performance. None lasted more than 8 to 14 months and then, either they stopped to work, lost valuable cumulative data, I got bored or else...until I fortunately found this one! I have now using it app for almost 3 years and must say I found the right combination and look else no more. No need to. I travel a lot on some 10 different locations in three continents, each year, and run about 40 to 50 kilometers per week. Here is my "rock solid, right combination": A. MapMyFitness App B. Wahoo Blue HR C. iPhone Look else no more, this is it. Good running! Fred