When I bought this item, the price was only slightly more than buying the Wahoo Fitness Key for iPhone
on its own so I went for it as I needed an ant+ compatible belt as well.
However I had no end of trouble with the belt; yes, it's comfortable, but false spikes (up to 300% of my max heart rate) or readings of 0 were almost constant and very annoying. Further research indicates that some people have a problem with the soft type of heart rate belt (which this pack comes with) due to insufficient connectivity between the belt and the user. I am obviously one of those people! I tried using water and gel to solve this but to no avail.
I now use the ant+ key that came in this pack with a Garmin Heart Rate Monitor For the Forerunner 50/405
which I have had no problems with. I don't mind this but would if I had paid the current price for the pack which is substantially more than buying the key on its own.
The ant+ key works well with wahoo's own app (as you'd expect) but also with endomondo and digifit apps. Connectivity with the belt is excellent and I have no problems maintaining the signal within a 10 foot distance of the iPhone.
If I were to purchase again I'd buy the key on its own and a separate 'old school' ant+ belt - not as comfortable, but (for me at least) more reliable.