OK, so in order to detect power loss, I'm going to try hooking this: http://www.isocom.com/datasheets/db92449.pdf ISP814 to my 120VAC, 60Hz line (with roughly 150k of resistors) to limit current.
On the other side, the idea is to connect to one of the Arduino's digital I/O ports, using the pull-up. But I have at least one (possible) issue on that side: the ISP814 is using two inverse, parallel diodes to keep it lit as the AC cycles, but as it crosses zero, I assume neither will be lit. Thus, I think I need a cap and possibly a resistor on the side connected to the Arduino (across the ISP814's pins 3 & 4) to "smooth" the output, right?
Any ideas/help would be much appreciated! -AJ