Thought I'd let everyone know that AVRCP works 100% for me now! I stumbled upon the feature accidentally when I was working out at the gym yesterday (I bumped the skip track and it worked). So I searched online today because the last I checked it wasn't enabled. The headphones I'm using it with are the Rocketfish (BestBuy) brand BT headphones. Then when I got to my car, I disconnected from the headphones and connected to my Pioneer 9800BT deck and the skip track button worked there too! I was very excited to discover this but perplexed at the same time.
So today I hop in my car and decide to try the skip track and it doesn't work. So now I'm wondering if I was just high on crack yesterday and imagining it working. So after playing with it, I discovered that I have to pair it with the headphones first and then the other devices have full functionality. The reason it stopped working was that when I'm not using the BT, I turn it off via the swapbt app in cydia. As long as I keep BT enabled, it will work with both devices even after a reboot. The only time I had to reconnect to the headphones first is when I turn BT off.
My phone specs: Jailbroken 3G on 3.1.2 Bluetooth related apps installed: swapbt, iBlueNova and sbsettings toggle. Don't know if those apps have anything to do with it working though.
Know I'm new here but I'm happy to answer any questions that may help everyone get this feature enabled as it was really annoying that apple only enabled play/pause.