I need an alarm for my son's bedroom door

[Guest guest]

My 4 year old son used to call me(sort of) from his bed and wait for me when he

woke up in the morning or at night. However, he now just opens his bedroom door

and runs out, even in the middle of the night. We have a big house and I could

easily not hear him once he leaves his room (which is on a sound monitor).

Can someone recommend a door alarm? Preferably, I would like something to

notify me in my room (not the whole house) and make noise until I turn it off.

Also, I would like to be able to turn off the alarm silently so that it does not

simply go off every morning when he wakes, or wake him up in the process. I

guess this is a tall order, but any suggestions? Thanks.

Caryn