They also act as Surge protection as well.
I`ve got 2 1200VA UPS`s, One which should cover My PC, 40"TV & Sky box & the other for my Main PC.
I`m considering Purchasing a 2000VA UPS for my Fishtank so that the filter will continue running in the event of a power outage.
They will allow you a chance to save & shut down everything safely......& I hope save any damage to things.
There maybe other uses folks can put them to, use your imagination.... A portable DVD player, a small LCD TV, they`ll run these for a little while dependent on the VA rating.
Batteries shouldn`t prove to difficult obtain when then fail, I believe they are Lead acid gel type batteries (at least in the Bigger & Heavier UPS`s) so similar to those in Alarm panels, so they should last for years.