I own a small WISP and need an UPS in a small enclosure at the bottom of my towers to provide temporary power for when the grid drops for a few minutes/hours.
This is often coupled with a multi-port POE injector from Wifi-Soft and a router for a WISP tower location.
This comes to $387 for an outdoor UPS with a run time of about 8 hours without power for 2 - 8 watt radios and a RouterBoard.
Here is a similar version of what I have described.