I have a 2007 E-320 and want to use the "Command" system for a cell phone. I can add a bluetooth adapter or a phone cradle, or a combination of the two. A phone cradle provides full use of the car antenna but it has to be plugged in to work. The bluetooth unit works only on selected phones. Either way the cost of an adapter is about $400 and a new Motorola Razr will cost $100. Do I have other (and better) options?