I have had the Zumo 550 for over a year now, used with a Scala Rider Bluetooth headset, Schuberth S1 and Nokia 6300.
The Scala system details are here:
CARDOSHOP
I have the basic system (mono & no radio) and it was around 100 quid from memory.
I think there is also a bike-to-bike system available so maybe worth checking out.
There is a base unit which clamps to the side of the helmet and has wired headphones which fit into the lining, the mic is also fixed to this on a boom so I would imagine it would be good for a flip face lid. The actual bluetooth part is a detachable pod which clips to the base unit and is easily removed for charging.
I actually hacked the base unit apart and fitted a 3.5mm jack to allow in-ear headphone use which means I dont have to have volume anywhere near as high to hear instructions and also cuts down wind noise.
IMHO this is an almost perfect setup as the Zumo works well with both other devices after pairing.
My Zumo is powered from the bike and whole setup is good for 6-7 hours use before recharge - tested on London to Le Mans runs in 2007 & 2008 plus countless 3-6 hour continental forrays !
The only drawbacks I have found so far are:
- Zumo MP3 are mono only (pain to convert and sound a bit flat)

- Phone Bluetooth connection drops sometimes on incoming call
Hope this rambling helps (my 1st post, so be kind)