I'm watching the video Debugging Backwards in Time, a Google Techtalk video by Bill Lewis. He's so neat.

He created the Omniscient Debugger (ODB) which has the idea that by recording every state change in a program, you can go back in time and see the exact state of the program at any time point. This would be so useful for debugging. How about implement this for Ruby on Rails? It's a little hard to debug and profile RoR code, and with this, you could have a powerful auditing and debugging system.