Home security system recommendation

I want to purchase a DIY wireless home security system. For the moment, I do not want to pay a home monitoring service and prefer to be informed of my alarm status via the Internet (WiFi and cellular) and text messages. I’d like to have the ability to connect to a monitoring service in the future. The main entrance to the house is a steel gate (http://i.imgur.com/E5g9kjI.jpg). I’m not sure if a sensor exists for this type of entrance. I have 3 solid wood doors, 1 aluminum door with window, many aluminum horizontal louver style windows (http://i.imgur.com/1JQCL9w.jpg) and a couple of glass horizontal louver style windows (http://i.imgur.com/LimU2kf.jpg). Also, I have an indoor cat. I wanted some input on what types of alarm systems and sensors you guys recommend for this setup to work and I can install. So far, I really like the SimpliSafe (http://simplisafe.com/) system, but doesn’t offer ZWave or Camera support, which is something I would like to add in the future.