My networking closet is finally complete! The latest addition? A UPS. Turns out, if you're really space confined, you have to stay in the DC domain and pretty much nobody makes UPSs for DC applications. Fortunately, pretty much doesn't mean no one. A California based company makes all these small DC centered power supplies for computers, and they sell a UPS called the OpenUPS that takes any battery, and you can create any sort of weird DC system you need. Runtime is about 3 hours with the 100wh battery.