I tried the SimpliSafe system, and was not impressed. We wired each door and window downstairs, as well as a motion detector and a glass break detector.
The problem is that when a sensor shows that a window is open, it is almost impossible to figure out which window if you have more than a few. If someone is coming in to my house in the middle of the night, I would sure like to know exactly where, so I could "greet" him. Me and Mr. Glock, that is.
Plus, the control panel is not back lit, and the characters are so small that they are difficult to read if you need even mild reading glasses.
So I threw it out and got a "Z Wave" system, also very easy to install. Mine is made by Samsung,and goes by the name "Smartthings".
It is accessible with your smartphone, and can be turned on or off remotely. You can add all sorts of sensors, cameras, thermostats, etc.
Very easy to install, and numerous companies make the sensors and the overall Z Wave systems.