Hey Volker,
* create a GraphAPI object using the app access token (let's call it @graph)
* to create the app request, use the new GraphAPI#put_connection method -- something like @graph.put_connection(user_id, "apprequests", :message => your_message, :data => your_data)
* reading the request should just require a call like @graph.get_connection(user_id, "apprequests")
I haven't had a chance to try this out yet, so let me know how it goes. If that works we might add it to the wiki as an example of using put_connections :)
Best,
Alex