illamint: the feature is sold as "comfort access keyless entry," and it allows the driver to start the engine without inserting the electronic key. (Without this feature, the default setup for BMWs is that the driver must insert the electronic key before starting the engine -- a form of two-step authentication that isn't susceptible to the attack described in the article.)

FWIW, I know about this firsthand because I bought a new BMW last year and I was adamant about not having the "keyless entry" feature -- for security reasons. The BMW salesperson acted like I was a bit crazy.