Or something like this:
#include <GUIConstants.au3>
Opt("GUIOnEventMode", 1)
$FakeWindow = GUICreate("")
$MainWindow = GUICreate("Screensaver", @DesktopWidth, @DesktopHeight, 0, 0, $WS_POPUP, $WS_EX_TOPMOST, $FakeWindow)
GUISetOnEvent(-11, "_EventHandler")
WinSetTrans($MainWindow, "", 1)
GUIRegisterMsg(0x0100, "KEYPRESS")
GUISetState()
While 1
Sleep(1000)
WEnd
Func KEYPRESS()
Exit
EndFunc
Func _EventHandler()
Switch @GUI_CtrlId
Case -11, -3
Exit
EndSwitch
EndFunc
Func OnAutoItExit()
MsgBox(0, "Exit", "A key has been pressed or the mouse has been moved. Goodbye!")
EndFunc
?