An alarm system seems really cool, definitely a project I will look into.
And yeah, an Arduino isn't really needed with an RPi but I have seen many projects incorporate both, mainly projects dealing with robotics (which is what I am interested in). In the long run I plan on making an autonomous robot. I don't plan on buying an Arduino immediately, probably after I've experimented with the RPi enough and run into some limitations. But that Microcenter deal looks pretty good, I might pick it up from my local Microcenter soon or just order it to save myself from the 45 minute drive.
Thanks for all the help everyone.