Looking for the best Wireless Security System

My husband and I were talking about getting more security in our home. We have had some weird characters move into our neighborhood recently, and we decided to beef up our security. We went on line to check out wireless security systems. There are tons available. We just haven't figured out which is best for us. I want one that you can put on the doors and maybe the windows too. I'm looking for the best price. Does anyone have any suggestions?