Notification Center is a Prefs Pane that allows you to perform actions when you lose your wireless connection or your computer sleeps or wakes or a Bluetooth device comes in range or different applications launch or quit.
Actions that can be performed are shell scripts, AppleScripts, playing a sound or simple opening a file or application.
What's new in Notification Center
Fixed a bluetooth bug Added actions to be performed for connecting and disconnecting from different wireless networks. This allows you to move from one place to another and automatically have different scripts executed when you change wireless network.