This is an open source system for integrating wireless Arduino sensors to an awesome home automation platform called OpenHAB. It allows you to get email notifications and audio alarming based on sensor data. The OpenHAB platform provides the mobile app server, browser based interface, actions (emails, Android/Apple push notification services), and rules engine needed to do real home automation.
This first demonstration videos shows a long battery life Arduino reed switch sensor integrated with OpenHAB's dashboard interface. It also uses the email feature and audio alarming feature.
This second demonstration video shows how much functionality and flexibility can be packed into a single Arduino sensor. This one monitors
1) smoke & combustible gas
4) sound (dog bark)
5) light level
6) temperature & humidity
Sketches and configurations: