If you want to get notified on Ubuntu whenever your webcam is on, then install Camera Monitor. Once installed and launched, a notification message will appear on screen displaying the status of your webcam (On/Off).
Camera Monitor is designed to run mainly on the GNOME desktop, but it is also supported on XFCE and KDE.
To install Camera Monitor on Ubuntu 11.04/10.10/10.04, launch the terminal and issue these commands:
sudo add-apt-repository ppa:phobosk/phobosk-ppa
sudo apt-get update
sudo apt-get install cameramonitor