Yep, pulley and string simple as that.
You will need:
4 pulleys (can be done with 3-5)
string or fishing line(enough to wrap up the wall, across the ceiling, and down the other wall)
Drill & Screws
Here is a video of it in action:http://www.youtube.com/watch?v=6PJW3t2bJpE
If anyone has ideas that would improve my idea please let me know. I would like a cheaper, lighter, smaller pulley that can directly connect to the wall.