Drmn4ea:
ST makes a booster - L6920 - that is about the best I've found in terms of quiescent power consumption (down to some 20uA or less depending on input voltage) and low voltage startup behavior. This will run down to 0.5V or so (actually, 0.4xx V in practice if you're not drawing much current). Not sure how low in cost you want to go; there are definitely cheaper ones out there if you don't mind higher idle current.
That's a pretty cool part, thanks! $2.33 from Mouser. Not too bad, though I probably would give up current to get down to something like $1-1.50. And then, uh, I have to confront the dreaded TSSOP8 package.
Drmn4ea:
Do you have any plans or schematics online? I'm also working on a very low-powered Arduino variant geared toward energy harvesting projects; might be good to compare notes.
I am just starting this journey. I built my first regular-power Arduino Clone, and I'm putting it through its paces (just discovered a bug today!). Next up, I am going to take the 3rd PCB I got in the set and build it out as a 3.6V 8MHz unit with no power regulator. I'll hook that up to 2.4GHz Transceivers, and start running tests to see how long they last, and who fails first. (Radio or uC. The datasheet says the radio goes first.)
Thanks for the pointer to your blog, I am going to dig through it!