I was browsing the web and stumbled upon this interesting article out of MIT. Here is an excerpt:

Recharge yourself and your electronics while relaxing with friends outdoors in Killian Court.  The MIT SOFT Rockers are smart, clean energy charging stations disguised as outdoor rocking lounge furniture.  Unlike conventional ‘hard’ urban infrastructure, The SOFT Rocker leverages its environment in a dynamic manner by using the human power of balance to create an interactive 1.5 axis 35 watt solar tracking system. Soft power electronics designed for this project charge the 12 ampere-hour battery and store solar energy harvested during the day. Put your body weight in play with an interactive, real time energy harvesting feedback loop that senses how you orient the rocker to the sun. Charge or run any USB device from speakers to cell phones and bring your friends to enjoy cool lighting loops at night for social gatherings.

Click the link below for the full story.

http://arts.mit.edu/fast/fast-light/soft-rockers/