I have a set of Sony MDRZX550BN bluetooth headphones. The headphones have a play/pause button and sliders for FFWD and RWD. The headphones pair fine with my Samsung Galaxy S4 running Android 4.4.2 and music plays fine. But I cannot get the buttons to work with any app, including the stock music player, Google Play Music, Spotify, or BeyondPod. I tried looking for an app that would work with bluetooth headsets and pass the control inputs to a music app, but it seems all those apps are designed for wired headsets. Any suggestions?