The comfort of the Polar H7 WearLink heart rate belt is used well. I use the heart rate belt with an iPhone 4s and the runtastic PRO. The pairing of the device has run at all. So far I have found no disconnections and everything works fine. I'm very satisfied with this combination. However, you should check before buying if the smartphone actually Bluetooth 4.0 beherscht and the respective app supports the pulse belt!