So you'll need a few things for this, first you'll need to search eBay for "Motorcycle Intercom". Amongst all of the really good (and expensive) intercom systems, you'll find the very inexpensive (usually around $25.00 shipped) wired intercom systems that use standard 2.5mm cellphone headsets. These can probably be used for other things, so don't throw them away, but put them aside. We wont be needing them.
Next we need the Jabra A210s (or any bluetooth to 2.5mm wired adapter). I found these cheap ($20 each) at cell Xpo, link
, so I used them over the Cardos, which were about $50.00 each. These will plug into the motorcycle intercom module where the wired headsets would have plugged in. See what we're doing here?
In my intro page, I mentioned that very basic soldering is required, but if you get one of the el cheapo intercom systems and find that the connectors are 2.5mm, you actually wont need to do any soldering at all. Mine is actually different from the ones most commonly found on eBay, and had 3.5mm jacks, so I needed to adapt the 2.5mm jacks to the 3.5mm ones on the intercom.
Lastly, you'll need to buy a couple of standard Bluetooth headsets. If you're in the states you're in luck. Recent legislation in my home state of California has required that anyone using the phone while driving do so with a handsfree kit, which means a bunch of online retailers are making great deals on Bluetooth headsets. I got a two pack on buy.com for $20.00.