Binary package “xautolock” in ubuntu precise
Program launcher for idle X sessions
Xautolock monitors input devices under the X Window System, and launches a
program of your choice if there is no activity after a user-configurable
period of time. You can use this to automatically start up a screen locker
if you have left your computer unattended for some period of time. The
program launched need not be a screen locker such as xlock.