From the NannyMUD documentation

LAST CHANGE

2000-12-11

FUNCTION

NAME
        query_idle - give time since last command from a player


SYNTAX
	int query_idle(object player)

DESCRIPTION
	Returns the number of seconds that an interactive player has been
	idle, ie the time since the last command was issued.	


NOTE
	This is only relevant to interactive players and are not implemented
	for npc's.