Processors used in alarm systems.

[Radiohead]

I am constructing a domestic alarm system for my final year project at
university, and would appreciate some advice. (Please bear in mind that
I am a novice on this subject, and I apologise if this seems like a
stupid question!)

Part of my project involves comparing my system to other commercially
available systems.

I need to compare the "brains" of my system to what would be used in a
typical domestic system, so I would like to know what kind of
processors would be used. Is there a thing as a typical chip that would
be used? Are there chips made specifically for alarm systems?

I'm still planning my system at the moment, and I intend to use several
PICs - perhaps 16F84 or similar - programmed in C. How advanced are the
chips that companies would use? I'm guessing they wouldn't program
individual chips themselves, so what is the process they would go
through?

Many thanks.