I spent a lot of time trying to push my changes of the logged in users configuration to the server. With the help of Christoffer, the problem was fixed and the changes to the configuration made from the app can now be pushed to the server. This means the app can now remotely control the state of a desktop Stoff player!
Solving the request authentication problem. It was very hard to debug as the problem could be on either the client or server side, or even both. We discovered that my OAuth library signed the request in a slightly different way than the server expected, which resulted in the server denying all requests except simple GET requests (which were used to retrieve the current configuration). This was fixed by packaging the request in a different way that allowed the library to sign it correctly.
This week I will make sure all the interface elements currently in the app are correctly hooked up to the configuration, so that all buttons and sliders actually affect the desktop player being controlled. I will also create a new design of the GUI, keeping in mind that the app should look native to iOS.