This project involves creating the circuitry for a wireless door sensor.
What this whole project is about is creating a magnetic door switch that will detect when a door is opened or closed. The big issue here will be battery life, we want it to be 2 years.
There will be four major components - a standard magnetic reed switch, an atmega / Arduino processor, a radio, and battery with voltage sensing (need to know when to change battery).
Very similar to this project:
That example project wakes up every minute to send temperature, we don't want to do anything unless the door is opened or closed. If the door remains closed we want the system to sleep and not do anything.
This is the radio we need to use: