Since I didn't see it mentioned in the other posts, I thought I'd add that the apcupsd installer places an application--apcupsd.app--in the /Applications folder.

When launched, no dock icon or interface window will open. Instead, your only indication that it is running is the appearance in the menubar of a generic UPS icon. Should a connection failure occur, the icon will acquire a superimposed red '?', and hovering the mouse over the icon will reveal the tooltip "NETWORK ERROR". Clicking on the icon reveals the available interface options.

The GUI's available functions are pretty much limited to status and event monitoring, and provide no equivalent for issuing the CLI commands. It is handy, though, in that it provides the ability, via the preferences settings, to add additional monitors for multiple networked devices, and to turn Growl notifications on and off for them.

Just in case someone else is having the same difficulties I encountered, take a look at your UPS cases.

The battery backup I couldn't get apcupsd to find--among the several it did find--was labeled "Belkin."

D'Oh! <forehead slap>

The NUTS software I referred to in a previous comment, does support various Belkin models as well as APC models (and others).

See http://www.networkupstools.org/compat/stable.html