Use a bluetooth headset for media audio on a Nexus 7 running Android 4.2
There is an app called Mono for Bluetooth that allows you route the devices sound via mono bluetooth headset. I'm sure there are other apps, but this is the first one I found and it seems to work fine. It also does the following:


sound indication when routing is switched on
restores sound volume after switching off the routing
indication when routing is on in status bar
restores bluetooth routing after phone call


Supports Android 2.2 and higher.