Simply put, the MK20 is a device that can be used to place and take calls without having to touch your phone at all. Of course, the use is limited to your car, just so you concentrate on driving for a change. The device comes with a mic and speakers to facilitate the whole thing. The device has a magnetic spot at the back to attach it to the sun visor clamp. What’s cool about this is that the device is so light that a strong magnet keeps it place, yet doesn’t require much force to detach.
The MK20 has a 2.2-inch LCD screen, which can be adjusted in three steps. It has three buttons hugging the screen, for call, cancel and hotline. Once the device is thoroughly charged, you will need to pair it with your phone. It’s very easy! Press and hold the hotline key, and the Bluetooth receiver will be activated in a couple of seconds. The blinking blue light next to the screen indicates it's live.
Next you'll need to look for the device using your phone, and while pairing, key in 0000 to seal the deal! Next click on the 'connect to device' option in your phone and you are ready to go. The coolest thing is that you don’t need to repeat all this every time you want to use it. Just pull the screen out and it will automatically form the connection in a matter of seconds.
Here is a site that sells only the top 10 Bluetooth Headset models. They also have information about hands free laws in various states 
