Uninterruptible Power Supply

Sycraft
If you need audio stuff plugged in, you'll need a sinewave converter. Those are very expensive from Tripplite and APC. Cyberpower makes a cheap sinewave unit that has really good output, however their quality control is not up to the standards of the other two in my experience (that said, I do personally have a Cyberpower unit right now).

To clarify, Sycraft is referring to a UPS unit with a "pure sine wave" output, as opposed to a "modified sine wave" output.  The latter is what most units have, as this is cheaper circuitry.  A modified sine wave is basically a stepped square wave.  This can introduce harmonics and noise into audio circuitry.  However...here's the catch: if the audio device gets its power from a switching power supply, then it should be fine; little to no noise should be introduced.
 
Now keep this in mind also in regards to a modified-sine wave type: the UPS unit only outputs this while on battery power (if a type that transfers once wall power is lost rather than remain online). Therefore, even if there is noise introduced into audio electronics while on battery power, you shouldn't be recording anyway! The UPS, for most people, provides emergency protection and time to stop what you're doing and save your work, then shut down your computer. It also allows for modern synthesizers to finish an OS update, for example, and not brick.
 
Now if you have super-duper, high-end stuff (or vintage analog gear) and worry about the modified sine wave, then by all means get one with a pure sine output. You've already invested thousands of dollars into your gear, so don't be a cheapskate!  Also, be sure your PC's power supply is compatible with modified sine waves. Some brands will shut down instantly!
 
Believe me, I've thought about this...maybe a little too much!  However, I still have not yet pulled the trigger on a UPS unit! Most, if not all, of my gear gets its power from either wall, desktop, or internal switching-type power supplies.  I've been eyeballing Cyberpower and APC 1500VA units.  A $35 difference exists between the two.  While Cyberpower gets favorable reviews, APC is the more "known" brand.

I am not from music world, but after many years in science labs where power cuts are more or less regular, I am skeptical about all such units.
 
I must admit that these units really protect against  strange glitches on input power. I can remember: 400-500V spikes, regular drops (for several msecs every 2 seconds), hi frequency "injections" and continuous "under voltage". Each such accident has killed at least several devices, but I can not remember any damaged device behind UPS.
 
But in complicated environment once the power was down at least something always went down immediately, even including big disk arrays with build-in battery connected to external expensive UPS. Typical problems was:

• the battery in all such units aging really fast, it should be replaced every 2 years, sometimes less
• not every device survive the switch time without rebooting
• this equipment is very sensitive to overheating
• these devices can break themselves
• (may be most important!) depending on local rules, it can be forbidden to use such units because of fire team prescription. In case you see "Emergency power off" button somewhere in the building, that is normally the case (since UPS will "ignore" such buttons). For private places with insurance in case of fire, that also can trigger unexpected conversations once used...

At the same time, there was no cases when I had nonrecoverable corrupted file system after unexpected computer power off. Currently opened files are normally corrupted, but the rest is ok. It is by design of modern file systems (used by Windows NTFS, while not the best in that respect, still has that protection). The data are written in "transactions", so in case at some point the disk is down, it is possible to find which operation was unfinished and return to the last known point.