Your 2005 is pre-wired for a phone. This is not an item that has to be installed at the factory. It does however require a large number of components to be added to the car. I drive a 2005 E500 which was delivered on 10/29/04 and I had the phone (a V600) installed in late January 2005 at the dealership.
"Pre-Wiring" means just that: the "wire" is in the frame of the car where it is supposed to be and the dealer only needs to hook up the neccessary equipment to it and it will integrate perfectly.
The MB phone kit includes something like eight (8) additional pieces of equipment that need to get put in for it to work correctly with your COMAND headunit. Not the least important of these is the MB version of the Motorola handset which includes special software that allows it to integrate with the system in your car. A "regular" V60/V600/V710 like you might buy on Ebay or Amazon.com WILL NOT work with the MB system.
The full install takes about a day and costs around $2,400 or $2,900 depending on whether or not you get the voice activiation option put in (which I recommend that you DO get put in).
Its not cheap, but it works incredibly well. The reception, when the handset is plugged into the car (which connects the phone to an antenna power booster and the exterior antenna on your roof) is practically unshakeable. The integration of the handset with the car is also beautifully implemented. Being able to select your numbers from the COMAND headunit, or by voice is really nice, and the fact that it mutes whatever audio you are listening to and/or plays the phones ring tone loud & clear under any circumstances (via your stereo speakers) is a real benefit. I have missed important business calls in the past because I didn't hear my cell phone ring due to listening to the stereo and/or wind noise from my open windows. This will never happen again now that I have the integrated phone system. In my business, 3 or 4 significant calls that I get because I could hear the phone, as opposed to missing because I just had a regular cell phone sitting in the center armrest that I couldn't hear, could easily end up covering the cost for the complete install of the phone.
If you spend any significant amount of time on the phone while you drive it is worth dropping the cash and getting the full MB integrated kit installed in your car.
