Eric at HP Tuners is working on this. It's just an option to turn on the capability in the tune, then you would need to fill in and dial in the related tables.
No separate sensor is used. Only the WBo2s and an algarithm is used to determine % ethonol content.
I'm running a full E85 tune...all I needed was injectors and the tune. But I have to switch tunes if I go back to pump. Would be interested to see if this happens. Apparently everything needed is already here, just needs to be unlocked/figured out. More ethanol percentage and you might need injectors to keep up.