How to add message to state in OpenERP
It looks like the form class in the client has a message_state() method that displays a message in the status bar. If you look through the client/bin/modules/gui/window/form.py file, you can find several calls. I didn't see any easy way to set that message from within a standard module, so you might have to hack the client code. 
If you want to display a message from within regular module code, I think you're stuck with a pop-up warning dialog.
I have a very simple question. How to add own message to state on status bar?