My $0.02 is that UPS's should definately be a category of hardware supported by SuperUser, until you start talking about something more relevant on EE.SE, but at that point it's obviously not a good fit for Superuser.
Should be on topic:
- Swapping a battery.
- Discussing specs including run time, chemistry, performance, compatible batteries, etc.
- Programming/interfacing to it (like your question).
Should be off topic:
- Building one from parts.
- Anything that involves soldering parts within a UPS.
- Generally hacking a UPS from a hardware perspective, for example to use a bigger battery than what was included.