change user presence from api

With completely avoiding using XMPP at any step?

It is possible and there are many ways to do so. However, the best way heavily depends on what exactly you want to achieve.
Do you want to change user's presence status for his already connected real resources or you want to create kind of a virtual, new resource with a special presence status?
The first case means close integration with Tigase session manager, the second can be achieved via component which can activate user's "virtual" resources and set presence status for them.
There are other ways possible but we really need to know more about your case.

I have a similar problem to solve.

I need to do something like the second option. I have an external application which can talk to the Tigase Server. And I want some component to listen on a particular port, so that I can receive the BareJID and change the user's presence by logging in as a virtual resource.

Any help would be highly appreciated.

Thanks.