This project will combine an ESP8266 WiFi module with an IR LED to remotely control and turn on/off a window A/C. An Android app such as IfThisThenThat (IFTTT) or Llama can be used to automatically turn on your A/C when you leave work for example. This could save a significant amount of electricity.
I realize there are a couple of products already available that do this exact same thing (ex. Sensibo, Tado, and Ambi climate) the main differences between my project and those product are price and openness. Those products each cost over $100 while this project can easily be made for less than $5. Also, those products are closed source while this project will be completely opensource hardware and software.