D.B.
Hi J.,
I don't have a recommendation for a system or contractor, but whoever you choose, DON'T put their sign in your yard as a "deterrent".
I wish I could remember my source, but it was reliable, not an e-mail "pass this on or your computer will explode" type of thing.
The reason this is not a good idea is because companies generally install their systems the same way in each house to save themselves manhours of redesigning (which translates to money) and it also helps ensure their installers get it right by doing it as close to the same way every time.
So, if a thief has successfully breached a house with ABC security systems, they'll know what they're in for at the next ABC house. Some systems use infrared, some use contact sensors/switches, laser break beams, some are wireless, some are connected directly to the phone line (so if they cut the phone line, no alarm goes to the company and you don't know you're vulnerable). Knowing what to expect before breaking in will give the criminal an advantage in planning.
All systems have vulnerabilities (someone must confirm your need for assistance, police still have to get to you, which takes time) but I agree with their usefulness. I just caution you to keep your specific system private. If you'd like to announce you have additional security, you can buy generic "this home has a security system" signs at hardware stores or maybe Walmart.
D.