the current merc s class is running a hybrid system similar to the KERS (kinetic energy recovery system) used in F1.
they had a car that would brake automatically, using sensors etc to keep a safe distance from the object in front if it was moving or bring the car to a halt if it was a stationary object.
they decided to give a demonstration in a factory and invited all the bigwigs etc. long story short, something failed and the car slammed into the wall... woops. red faces that day. apparently being inside the factory affected the sensors - so they claimed. not sure if that has been developed further.
i know they have 'seeing' headlights and stuff now.
Nothing failed that day as the system wasn't turned on, you can read up about it all elsewhere. I've been using the distronic system for a few years now and so far haven't had any incidents. The yardstick has been the S Class for the past few decades but the time between the technology being fitted to standard vehicles is shrinking dramatically.