I don't think you can suppress the formkey check so all I can think of is skipping the "if form.accepts" and processing everything yourself.
You also might want to have a look at XMLRPC which is sort of designed for this kind of thing: http://web2py.com/book/default/chapter/09#XMLRPC The new REST capabilities might work as well but I couldn't find detail on POSTing into them: https://groups.google.com/d/topic/web2py/gcqEcXIo7RI/discussion
