How about this gadget I bought from Modern Device? (see attachment)
It provides 3.3V from a single AA battery. And the active components are so small I initially thought they were a speck of dirt (see second photo, parts circled).
According to their site:
The input can be anything from 1.0 to 5.5V, so this can also be used with 2x or 3x AA battery packs (even 4, if NiMh), and it will continue to work when hooked up to a 5V power supply. The regulator will work down to less than 0.5V and can squeeze the very last bit of energy from the battery.
I have no connection with them, I just thought it was interesting. If you want to squeeze energy from your batteries, and you can use 2 or 3 AA batteries, this could be the thing for you.
