He’s using an Arduino Uno and an Ethernet breakout board to hook it up to the network. This allows him to send text messages to himself when the alarm system is armed, disarmed, or triggered.
This board also features 128 MB of RAM, 8MB of Flash and the usual compliment of Arduino pins in a Leonardo-compatible layout. Also on the SoC is a PCIE bus, Ethernet, a USB 2.0 host, and an SD card.