Energy from children

With all the hubub about the power-generating playground equipment from BYU's engineering department, lately, I have a few ideas to add to the clamour (rough sketches coming soon)- if somebody else decides to pick these up and build them, I only ask that they use it for benefiting those who most need it, rather than lining their own pocketbooks. And so:
- A "water wheel" - something like a cross between a ferris wheel and a slide. (This will probably make more sense when I've learned to upload drawings).
-Put a ratcheting joint in the top of a swing set - so every back-and-forth moves it along a little further
-Capturing the friction energy as children slide down a slide
-A trampoline-like cushion-like toy that has air underneath (many baby toys are built on this principle); whenever you jump down, this could force a piston along a chamber; made of sufficiently springy material it would bounce back on its own
-A dumbwaiter-type device, perhaps two buckets - a child goes down, the other side comes up; the damping device at the top also serves to collect the energy released each time

More, possibly, to come.