[Asterisk-Users] Extension "follow me"

[Asterisk]

We are going to have people in our office who do not sit at the same desk
throughout the day (or week), and have Cisco 7940 phones using the SIP
image.

Is it possible to easily set up the phone so that they can enter their
extension number and password on the phone, and thus have their extension
follow them ? I know that you can change the sip settings, but that requires
admin capabilities.

I know that this is similar to follow me, but person A might be at B's desk,
while B is at A's desk, so I can't use call forwarding, and I don't want to
ring  x number of extensions in order to find the person.

I really want to "find the extension"

Julian.