I don't know if you'll find battery operated heaters ... may draw too much for typical batteries to do any good. You can get a simple battery operated air pump ... for Irene I bought two at a pets supplies, though LFS should carry them. If your tanks are large enough 20gal + and stocked reasonably enough, there's enough natural gas exchange to keep your fish alive. Stirring the surface with a stick, spoon etc will better promote gas exchange.
When I lost power I just boiled some treated water and mixed it with removed tank water to cool it down before I poured it back into my shrimp tank. Not the most ideal way, it works better for smaller tanks where you remove smaller amounts of water. I'd hate to imagine doing this to keep 125gal tanks warm.
