Newbie here, questions on this alarm trigger project

Hi guys,

Got a question on whether this is a good idea and/or feasible project.

I'm thinking of getting the Arduino Ethernet, have it plugged to my router and draw power from the ethernet cable.
Then somehow tap into the home alarm trigger, so that when the alarm kicks in, it would run my code.
For now I'm planning to send an email to myself as a starter, but later I'm thinking of sending commands to cameras and have them start recording stuff...

I'm pretty sure this is do-able, can someone tell me whether using the Arduino Ethernet is good for this? Also anyone know how to make the trigger? Or is simply tap the signal wire to the IO input (maybe need to get some resistor to get the triggering input right?)

I'm new to Arduino, but not new to programming.

Thanks!

I'm no expert on the Ethernet side, but on the connection to the alarm you should perhaps consider an opto-isolator which will make sure the alarm signal is electrically separated from the Arduino. The output from the isolator will just be a normal digital input. You code will be looping forever, reading the pin on each pass, and if it's (say) low, kick off the appropriate part of your code.

Hi, would "Arduino Ethernet Shield Rev3 WITH PoE Module" be a good board to use for this?