Harvesting energy from human activity

Just found this via Digg:  the Japanese are researching ways to generate electricity from people walking thru train turnstiles.  I’ve often thought that so much of what we do is wasted energy.  Every time I go to the gym and watch people using treadmills and stationary cycles, I think about how stupid it is that all of that energy is just being wasted.  (I also get a mental image of a bunch of hamsters running on hamster wheels though, so it could just be me   If I owned a gym I think I’d seriously look into finding a way to harness that energy to at least run the gym itself.  Doesn’t it seem like we humans spend an awful lot of time doing things that could be used to generate energy?  I mean, even though it’s not a lot, couldn’t my keyboard be taking the energy from my fingers hitting the keys and storing it in my laptop battery or something?