HardwareGrowler is the best way to find out when hardware status changes on the Mac. If you need to know what's going on with your Mac, then you need HardwareGrowler.
When your power cable unplugs, HardwareGrowler will spring into action and lets you know about it.
HardwareGrowler will also let you know about changes to networking on your Mac. When a wireless connection changes to a different access point or an IP address changes, you'll be notified about