I have the SENA SMH 10. It is pretty awesome. My wife and I have a set, and it is one of the reasons we are still married
They consist of 2 parts. There is the bluetooth unit itself and "Clamp" or mount.
The Bluetooth device clips to the Clamp. The clamp has the mic and speakers wired to it.
They make several different clamps. One has speakers, and another has a headphone jack so you could plug in ear buds. These clamps are relativity inexpensive, so if you have 2 helmets, you can move the SMH 10 from one helmet to another in seconds.
The also have another device that is essentially a bluetooth hub... It is called the SR10.
It allows you to plugs a 2 way radio into it, and then have it work wirelessly to your bluetooth headset.
It has a PTT button that you can mount on the handle bars.
So you get the functionality of the older wired system, except it is wireless, and less money!!
I mainly use my SMH 10 for listening to music on my phone. It also works for searching for a particular place, and then navigating there. It is also easy to take phone calls, make phone calls, and believe it or not, send text messages!!!
The newest firmware, that just came out today, will let you have a 4 way conversation with other smh10's.
Hope that helps!!!