I've been noticing periodic dropping of my BT connection between my Garmin vivosmart HR watch and the iPhone 6 Plus. I also have issues with BT on my iPhone connecting to both my watch and my Toyota RAV4's system at the same time. I don't recall either issue prior to iOS 10.1, so there might be an issue with the 10.1.x. The BT connection between watch and iPhone drops out briefly but then immediately reconnects on its own without any action on my part. The only reason I know that it is dropping is because my watch vibrates and flashes a message telling me that it lost BT connection.