"I've been using a polar hrm for the past 8 months and found that by the time I have the hrm, phone, earphones & chest strap, I started to feel like somewhat of a transformer. I stumbled across the Wahoo running pack by accident and after some research decide to purchase it. I used it for the first time this morning. I can't say enough good things about it. The chest strap is comfortable, the iPhone with adapter fits perfectly in the armband (purchased separately) and is light and comfortable to wear. I was surprised at the amount of information the Wahoo app provides. I have paired it with the 'mapmyfitness' app and the two seem to work well together. I would never go back to using a watch style hrm after using the Wahoo running pack (unless of course I was doing something that wouldn't be suitable to have a phone ie swimming). The fact that I can now just strap on my phone and have my music, hrm, calorie counter and gps all in one unit makes the Wahoo running pack invaluable in my opinion."