I am about to evaluate a new BT system, STEREO , 500m B-B etc AND "sender unit" for non BT devices, and up to 3 device pairing. Claimed 8 hour
USAGE battery life ( which has always been my bugbear with BT ).
I Import/distribute the
StarCom1 wired system . Single curly cord can bring to each helmet :- Intercom, Stereo music, 2 way radio for B-B, phone, GPS ( or 2 music sources and 2 phones on the Digital ) and runs from bike power so it don't go flat.
More are asking for BT but I have not taken it on as all the feedback I have had is poor battery life and pairing only to only 1 other BT device.
I will report back after a couple of months of use.

Prices are looking similar to the interphone.