Can a pin handle a voltage greater than Vcc if it is just sinking to ground?

retrolefty:
Or are you not planning on actual battery cut-off, just some kind of a minimum current draw mode?

Lefty

That's the idea.....put everything into deep sleep mode and have a pin change interrupt that will wake everything back up again when it is time to turn back on. Its just a small GPS logger that my wife can wear on a lanyard around her neck when she runs. I'm trying to make it really small (my goal is for it to all be on one board that will fit inside of an "altoids smalls" tin along with the battery.