Wireless Security Alarm

(sorry for the caps, I just wanted to catch attention because this is an urgent question).

Recently three apartments in my complex have been broken into, and they were all robbed. So far, nobody has seen the perpetrators.. so they are out free and breaking into homes whenever they catch the opportunity.

I know some people are thinking “Just get a big dog”, but I cannot. I am expecting my first child in May and I cannot afford, spend the time on, or find a dog that will be great with an infant and be low maintenance as well as a great guard dog. I looked, but in the end I was not able to find a dog that would be good for my family.

Anyway,

If anyone knows any great wireless alarm systems that do not cost very much (no more than $80), are VERY loud, and would be great for doors (mostly the front door).. PLEASE let me know.

Thank you very much.

(ps. no rude or sarcastic comments please. Also, I am not shouting when I use caps.. please do not get offended.)