THIS WOULD MAKE MONEY!!!!!!!!!!!!!!!!!!!!!!
This idea is very similar to the machines that are used at gun ranges to shuttle the targets down range and back. The "cart" would sense the darts thrown and automatically move forward to allow the player to retreve them, and then return to the correct position and start over. I'm sure it would even be possible to design the system to keep track of scores, have built in storage compartments, or maybe integrated entertainment components like a stereo w/ Ipod dock, a video monitor, and/or just basic sound effects that coincide with the game play.