Door of Alarm
This seemingly innocuous door issues a shrill alarm when an unknown creature walks through it.
Wondrous Item 520 gp
You can spend 1 minute to attune any number of individuals to this door. When a creature other than an attuned individual walks through the door, a shrill alarm sounds and doesn’t stop for 1 hour, until that creature leaves through the door, or you command the door to be silent.
Published in Adventurer's Vault 2, page(s) 80.