Two benefits - 1) Additional battery power in a power outage and 2) Filtering commercial power.
I happen to have a pile of UPS backing up Alarm System, Camera System, (2) PC's, DISH DVR, TV and Phone/Voice Mail System.
A small UPS in the 500VA range is good insurance for power surges on something small like a scanner and will give you some time to figure out what's going on with the outage, not to mention the batteries in portable scanners. I have 1400VA UPS's on the PC's and scanners and another on the TV, as most power failures here are less than 30 minutes. Run time depends upon the devices connected.
Power strips that profess to be "Surge Protection" are pretty useless. Commercial power is getting dirtier and dirtier, and I hear my UPS "trip" 2 or 3 times per day in response to an aberration.
If you're bored or needing further information, try this:
UPS Selector Sizing Applications or just go to Staples and buy a 500/700 for $50 to $75.