This is a contact-type 3D scanner. Philippe “Philo” Hurbain (co-author of “Extreme NXT“, a book about advanced Lego robotics) made it to help him import odd-shaped Lego parts into the LDraw Lego-CAD program.
As you may have noticed, the scanner is itself made out of Lego. I think the only non-Lego parts in it are the actual needle that prods the thing being scanned, and one extra-flexible cable going to a standard NXT light sensor.
All the rest - drive components, sensors, you name it - is 100% Lego. The brain is Mindstorms NXT. Hurbain has made various add-on sensors for Lego robots, but I don’t think he’s used any of them in this.
Apparently, the new linear-actuator parts are accurate enough for this job, when you drive them with one of the NXT motors, which have built-in position encoders.
More info on Philo’s site.