I wonder if you could use this?
You could turn on this virtual timer switch under 1 of two conditions, the physical switch is turned on or motion becomes inactive.
When the virtual timer switch turns off, turn off the physical switch only if motion is inactive at that time.
That way the timer will count down from pressing the physical switch, but if you trigger motion and it is still active when the timer runs out, it won't turn off the switch, but will set / reset the timer when motion becomes inactive.
Simon
