Best platform for low-power collection of sensor data? I'm looking at having a small footprint device that would capture sensor data relatively steadily over a multi-week period, and don't have a lot of room for case and battery.  (There is some, but size/weight minimization is a good thing..) What recommendations would people have for a board to use for this, and any idea on the best ways to power it over that duration?  I would think just a rechargeable battery pack, but am open to suggestions.

Also, although the device would probably exchange the gathered data through wireless/bluetooth, I would want to keep that powered off unless a button was pushed, to minimize power consumption from that side.