How could I get presence information in web messenger?

I want to show the presence information and an icon allowing to start a chat behind a user name on different pages e.g. in this forum a user name is shown beside each post and I'd like to show if the user is present (= has the messenger open), the status (busy, dinner etc) and an option to send a message behind the user name ...

 

To my surprise I didn't find the presence information in the database?

 

How could I retrieve the presence information? Did I miss something in the database? Is there an API?

 

And: How could I directly open the chat window for a specific user (should act like the "Invite" menu option on the contacts list)