These are not cheap, but they may come in handy someday:


http://www.powerstream.com/ultra-light.htm



Interesting tidbit:


"There are microcontrollers that draw less than 1 microamp, such as the TI MSP430 in standby mode; so a 10 mAH battery could run these for 5 months between charges."

 

Very nice ! , thanks . I've been looking for something like this for a few projects that I have planned in the near future