How can keyframes of properties be added to an action? I tried to add keyframes for the emission value of a material to an action, but couldn't find out how. 

Adding keyframes for a object's location works as expected but properties like emission only show up in the Timeline and Curve Editor.

A MaterialAction is created (only visible in the NLA Editor) toggling to edit mode Tab the keyframes are displayed in the time line. This MaterialAction is not accesible from the Action Editor.



EDIT:

Fweebs suggestion to use a driver works unfortunatly only in the 3D-Viewport but not in the BGE. I didn't ask specifically for the BGE because I was hoping for a common solution that works everywhere.





.blendfile here
As the tooltip mentioned: 


  Edit keyframes in active object's Object-level action.


So I bet that is why it is not currently supported yet? 



However, you can still tweak it in the Dope Sheet mode, and use the Filter button to block other action types, if helps.