There's already a /stay command. It tells the pet to stop following you.
As the whole pet system is in it's infancy stages, I do believe much like you described will be implemented as that is the general idea of having a /follow command. It will follow you when you ask it to follow you. It will stay when you ask it to stay.
Not to be mean or anything, but there is a sticky of rules in the wishlist area. One of the rules is not to request obivious/commen sense type stuff.
Edit: Bah, Kary and her clicky fingers.