First, thanks to the info on this board. I probably would have never found endo without it. I am a recreational MTBer with flat trrails near my home. I loaded endo onto my Evo 4G and I really liked the program. Whether you like it or not may vary on your uses. I then wanted a HRM and decided one that BT with my phone made the most sense for me. I bought the Polar H7 at my LBS, but it does not talk to my phone. So, I returned it and purchased a Zephr from the Endomondo store. Good price and fast shipping.
That HRM links to the phone and works very easily.

Overall, I am very happy with both products and can recommend them to anyone.