The project was stared with a goal of creating a low-cost wireless PIR sensor by using Arduino compatible hardware and enclosure from already available cheap, less than $5, PIR lights you can find on eBay, like the following http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=wireless+pir+light+battery&_sop=15
- custom Arduino compatible hardware
- nrf24L01 2.4 GHz wireless module for communication
- 2+ years run time with 2 AA batteries