1. I need to be able to switch to next track in the playlist and change the volume. Is there some kind of global object I can use to do this? All I can find in the API is callback interfaces.

static_api_ptr_t<playback_control> pc;
pc->start(playback_control::track_command_next);
pc->set_volume(volume_in_db);

2. I need a callback interface class with a function that Foobar calls every update. Is there any class available for this?

class Thread : public main_thread_callback
{
public:
    virtual void callback_run()
    {
        // This function is being regularly called.
        // I use this function to poll data from an external input device
    }
};

class Timer
{
public:
    void start() { mThread = CreateThread(0, 0, &Timer::run, 0, 0, mThreadId); }
    void stop() { TerminateThread(mThread, 0); }

private:
    LPDWORD mThreadId;
    HANDLE mThread;

    static DWORD WINAPI run(void*)
    {
        while(true)
        {
            Sleep(1000); // Call interval of the callback_run function
            service_ptr_t<Thread> p_callback = new service_impl_t<Thread>();
            static_api_ptr_t<main_thread_callback_manager> man;
            man->add_callback(p_callback);
        }
    }
};

class Application : public initquit
{
public:
    virtual void on_init() { mTimer.start(); }
    virtual void on_quit() { mTimer.stop(); }

private:
    Timer mTimer;
};

static initquit_factory_t<Application> foo_initquit;

Thats what I want, and it accidentally works great as far as I know, and I don't!