I just got back from a trip to Mexico and one of my riding buddies had this for himself and his wife on the back.
BlueAnt Wireless North America - Bluetooth InterPhone motorbike helmet handsfree and intercom kit
The blueant "system", which unlike every other com system is just a device that clips on your helmet and has a speaker/mic. It works unbelievably well. It is brilliantly simple, no wires and only has one main button plus an up and down for volume. You can either pair to another blueant (like your passenger or a riding buddy), to a cell phone, or anything else bluetooth.
He mostly used it to comm with his wife on the back, but after she took a jet back to the states and we were left driving around Mexico, this thing was incredibly valuable to navigate around the crazy cities and a poor boarder crossing choice on the way back to Texas. The range is good enough to be practical at about 150-200 meters if it is clear and about half that if it is mountainous. We were using it pass trucks around blind corners in the mountains. It was awesome.
I've tried a couple of other motorcycle comm systems and none worked even close to as well (and all had wires, too!). I can't use enough superlatives to describe it.
Talk time is something like 5 hours active full-duplex communication or 7 or 8 hours on standby. We'd usually keep them off on the long days and flash the hazards if we needed to switch them on. We did a 700 mile day with plenty of juice left over using this technique.
It has two volume levels, normal and high. High is good if you ride with earplugs (which I do).
The only negative is that it kinda hurt my ear after a while because I didn't have a cutout like the Nolan. When I buy one (that i'll mostly pair with my cell when I'm driving around in the US), I'll probably cut out a bit of my helmet padding to make it fit better. Also, I understand that you can only pair two devices to eachother, so if you have 3 comms, only 2 can be paired together.
The cost is $144x2 at amazon.