Relevant code for the device is contained in Sensit2.1. Images for the new version of the device using the ESP8266 are in the Images folder. The website contains some photographs from the old device and original project, but the main page of note is jaloGraph.html and its related file graph.js.
The device multiplexes two force-sensitive resistors to measure log when someone is sitting and when they are potentially slouching.
The device also contains LEDs and an alarm which sounds if the slouching is detected for a few seconds straight.
The website is located at: https://sensitbme.herokuapp.com/jaloGraph.html