Steve, MB has memory functions now, depending on the model, with the next-generation smartkey. On 2001's remembers preset preferences on the seat memory and mirror angles, and climate control settings. Never heard of a key that changes engine mapping or speed limiter. Sounds like a good idea at first, until your kid needs the power to merge into traffic, or say avoid an accident at a traffic light or something. On the keyless-go, yes the card that is carried is a transponder, I believe the instructor said the person carrying the card grabs the door handle and pulls out on the handle, then it unlocks the door and unlatches it. I am not sure if all the doors subsequently unlock or not, probably programmable by the owner what all will unlock. To start the car, the brake pedal must be applied and a button on top of the shift knob is pressed. Also if I remember right, the transponder has to be within 4 feet of the receiver, which is located in each front door and the trunk lock. In regards to Blackmercedes comments about the smartkey, the IR and RF functions are purely for locking/unlocking and for the convenience features. RF is used for the locking/unlocking because it has about a 40 foot range. The IR is used for the convenience feature (convenience closing/summer opening) because it needs line-of-sight, MB doesn't want to be sued because you couldn't see if the windows were clear and decided it would be neat to roll up the windows anyways, in the process killing your pet who was in the car, but hanging there head out, or someone was stealing something out of the car and got trapped by the window. As far as the DAS, or driver authorization system, it is operated via a transponder chip in the key. The operating principle described to us was "challenge and response", maybe this is just another way of describing "dual encription", I'm not sure. We were told that a challenge is made via an algorythmic computation, and a correct response must be returned. This is done using no power on the part of the key. The proof of this is the wallet or emergency key that comes with the car. It is quite flat and contains a blade which is used to open the door. The key does fit into the EIS quite nicely, even though it is less than 1/4 of the thickness of the regular smartkey. The emergency key has no remote function and contains no battery, only the transponder required to start the car.....Gilly