Sorry, this will only work on short focal flange mounts, which basically means mirrorless. So, there might be an EF-to-EFM version, but never an EFS-to-EF version.
One more reason to support my belief that mirrorless is the future.
Why does it require a short flange mount? A telecompressor
is like an inverse teleconverter.
An optic free adapter such as an EOS to NEX, F to EOS, or M to X-mount all require the adapter to be of a precise depth to bridge the gap between the two flange depths, placing the lens at the correct distance to maintain the usual focus range.
However, optics placed between the body and lens such as teleconverters and the Canon FD to EOS adapter
overcome this limitation. As long as its got the correct distance from the lens to the telecompressor, and the rear of the telecompressor is able to project it's image correctly from its rear element to the sensor, all is good.
There is a diagram near the top of this page about the telecompressor in the Nikon E2
, and it indicates the lens focuses its image to a point far in front of the sensor - much like the way a teleconverter works.
As far as I can see, an EF to EF-S telecompressor is theoretically possible.