I can think of a few good project ideas for people to mess around with. I think it would be an excellent thing to have a "projects" topic to collect these, so that junior hackers can win science fairs.
Use a tessel servo module and one or two servos to drive/power/mess with some kind of multi-axis pendulum. Draw sinusoidal graphs in sand. BONUS: power a "Chaotic" double-pendulum and see how whacky you can get things to behave before the entire thing shakes itself apart
Using an audio module, find a way to detect shouting. When people are shouting, play a loud noise to stop them. BONUS: Record and play back the shouting. Or store it for later analysis.