call forwarding

I'm looking for an app, which would help me solve the following problem.
There is a gate, which can be opened by calling from one authorized phone number (let's say 111111111) to another. A gate receives calles on it's own number (let's say 999999999) and then - when the caller is identified as authorized, it opens. However, there are other people which need to open the gate. In order to do it, they have to call number 111111111 and ask the number's owner to cal 999999999 from their mobile.
What I would like to do is - install some application on the device with number 111111111, which could be controlled by other, authorized phone numbers - for example 222222222, 333333333, 444444444 and which would make a call from 111111111 to 999999999 on their demand. Is that possible?
In other words, I need the number which controls the gate opening, to work as server for a few other mobile phones.