It connects to one BT device only, a phone. GPS, etc should use wired connections. But, nowadays, GPS doesn't have wired connections and most headsets accept two mobiles.
So, can fw be changed in a way, a possibility to connect a mobile only, would be selectable, in order to connect GPS via BT??
As some headsets doesn't allow to connect too many devices simultaneously, but most, if not all, requires a mobile to be paired directly to listen to a stereo music.