The alita al-60 is a commercial type air pump that has a 3/8" output on it. I have it piped into a 1/2" pvc
system that runs around the ceiling and also outside to the back deck. It's supposed to run up to 50-60 sponge filters, I've only got about half that many going now.
As far as the battery backup pump goes, eh. I seriously doubt there would be a situation where it would be useful, I mean yeah, the power goes out sometimes, but the fish aren't all going to die immediately because of the lack of air. It could take several days depending on the surface area of the tank. I have tubs that I have kept outside all summer long with no pump at all and the fish lived just fine, although filtration/air pump is definitely ideal.
Either way, living in hurricane country, I've already considered what to do if we lost power for an extended period of time, and the solution was one of these
Honda Eu2000 Generator America's Farm & Home Store
Mostly because air pumps are the least of my issues if the power is out, I want the ability to maintain heat in certain tanks, as well as other things like computers, fans, etc.