Accelerometer to 2D game navigation, using [nodes]

So I have a doosey,

I'm making a binaural game where movement is initiated by a user leaning forward/backward and rotating with an accelerometer on their chest.
I've done all the audio but its just my movement mechanism that isn't working out.

I want leaning forward to initiate acceleration in the direction the user is orientated. The attached patch just features leaning in directions to move the xy coordinates of the node.

How do I convert my clean accelerometer data so that the 'roll' adjusts the 'rotation' of my node so that when I lean forward it will move that way in this topdown 2D view.