UPS shutdown happens how?

[Tom Horsley]

I just got a new UPS at work which has a USB cable connection.
If I look at the power settings in gnome-control-center,
it claims to know I'm on a UPS, so I guess it knows how to
talk to it.

I told it to shutdown when battery power is critical, but
I'm wondering who the heck recognizes that. I don't run
a gnome session, so is there some daemon that needs to
be working for it to actually shutdown cleanly?