Available in 1.6, 2 and 2.4mm focal lengths
http://www.vixenoptics.com/category-s/169.htm
AFOV is only 42* though which would make tracking a hassle in a non-driven scope and price is pretty steep. Still, an interesting development.
Hopefully this begins a new breed of ultra short eyepieces. If it weren't for the small field of view I would making room in the eyepiece case for these.