As mentioned, this project is a spin-off from my Home Automation and Security project, so some work has already been completed. The next stage is setting up tools to write and compile code for the ESP8266...

The main display unit consists of a small 1.8" TFT display, ATMega328 and ESP8266 module has been built and tested... The costs of the display hardware is less than $20....

Each ESP8266 WiFi Monitor Module should cost less than $5

While any type of sensor can be used, I will use an inexpensive piezo sensors (the output of which is analyses to prevent false alarm) and a simple IR reflector (to determine if door/windows is open or closed)...