[danshaffer]

we had a great roller-based grabber (like 100). actually, we had three. the SVR one was popping tubes!
we also used a gas spring instead of surgical tubing to take the load off of our arm, and allow us to use the window motors to move our arm, which did have two motors on the end of it for the rollers. the part is pretty unique... i'll try to upload a pic when we can get back into our lab later this week.
they may not be the most elegant features, but they're pretty useful.