I built this thing in a hasty panic the night before XMas because I wanted one of those cool time-lapse videos during the gift opening. Yes, Kyan got more than one gift. The goal was to capture a tracking shot lasting the predicted duration of Mommy, Daddy, and Kyan's wrapping shredding - I set the gear ratio and pully configuration to have the phone camera slink itself across the room over a one hour period. The NXT brick acted as its own little sedicam ballast.
More to be documented, but the video came out as cool as I imagined... will post