I setup a ZWave smarthome controller and purchased various motion sensors and lighting controls (ADT's systems are based on ZWave technology). I have both an ISY994i-ZW and a VeraLite controller that I use at two separate locations. I prefer the ISY device over the Vera (even though the ISY is more expensive) due to the ability to program it exactly how you want without much fuss. Vera tries to do too much for you and fails.
You can go as simple or as complex as you want. I personally started with a very simple system. I purchased enough motion detectors to fill both of the houses at the farm and set the controller to email me anytime there is motion. I also set them to warn me when the batteries in the detectors go low.
It all went so well I wanted to do more.
The house in back is a pre-Civil War structure that was wired for electric lighting later on. No switches were wired and all the light sockets have pull strings. So I got some ZWave LED bulbs (I really hope they last the estimated 25 years) and have the system set with two programs, one is for when I'm home, other is for when I'm away. When I'm away, the motion detectors only email me when motion is detected. When I'm home, the motion detectors no longer email me on motion, but turn on the lights as I enter a room (which they do not do when in the "away" mode).
Either system can be operated from any web browser on any device.
Since then I've also added other things like leak sensors and power relays so if there is water detected in the well cellar, the power gets cut off from the pump automagically. I also keep temperature monitors on the system to alert me if the fire in the well cellar goes out so there is no chance of freezing up of a winter.
I run the entire system on a battery backup device that emails me if the power goes out and when it is restored, and use a Cradlepoint branded router that allows me to use both a wired internet connection and have a cellular backup connection. Even put a motion detector in the back of the mailbox to know when the mail arrives.