Whether the keyguard is enabled or disabled.
The keyguard is the dialog requiring some sort of unlock action when the device is turned on.
Note: while keyguard is disabled, your SIM pin unlock screen may disappear after a few seconds after a reboot.
WARNING: while keyguard is disabled, the 'lock pattern' mechanism is also disabled, so your phone is unprotected if it is lost. There is also the possibility of interference with other applications that manipulate the keyguard.
On Android 2.2+, this action should probably only be used when the device is on and unlocked, unless the unlock method in Android settings is set to None.
Side-effect: coming out of Airplane Mode with Keyguard disabled may leave the SIM unrecognized until Keyguard is toggled again.
See also: action Keyguard Pattern.