Thanks for everyone's responses - but I think I need to clarify one point --
These two relays that are either open or closed, (#1 armed/disarmed or #2 normal/alarm activated)
are dedicated to notifying me - not to any other purpose in the system.
So I don't have to go about being somewhat careful in how I attach to my alarm system.
I could as easily light up an LED someplace based on the closed/open state of these relays.
My intent is to run wiring (or borrow pairs) from CAT5 wiring that already runs
from the alarm system to where the Arduino is -
I like the ideas some of you have for detecting current in the coil of one relay by magnetically inducing a smaller relay nearby,
which removes any actual electrical connection, etc etc.
Neat idea, and one I'll save for later consideration ;-)
In essence, I guess the question at it's simplest is this:
How can I monitor a switch to see if it's open or closed using an Arduino?
It almost seems that I could use this:http://arduino.cc/en/Tutorial/DigitalReadSerial
My thought though, is that I want to monitor TWO relays,
so that would need some modifications...
Do I have to consider the effects of my circuit being a larger loop (longer wires) circuit
than that simple 2" tiny circuit with a manual switch?
It would seem in that DigitalReadSerial example that the Arduino
is providing the power, in which case the gauge/length of wiring, etc
would have an effect on how much current the Arduino is being asked to source?
I guess if there are concerns for voltage/current being exposed to the Arduino, I could
use the relay in the alarm panel to just complete a circuit with a secondary power source
to close a reed relay that the Arduino is observing the contacts on....
Does that help folks understand how to help me more?
I really appreciate everyone's input --