We missed this announcement during the CES shuffle, but Adam actually brought it to our attention. Metabones is a new optics company that has created a lens adapter for Canon and Nikon lenses for use on Sony E-mount cameras (like the NEX series). Other unofficial lenses exist to bridge those standards, but what makes Metabones' different is the inclusion of proprietary optics--a focal reducer--in the adapter that adjusts the light coming from the lens. This basically acts like an inverted optical zoom, shrinking the image coming into the objective lens to fit into the APS-C sensor. With other adapters, you have to settle for some additional cropping when using a non-standard lens, but Metabones claims that its adapter will give you full coverage of your Canon EF or Nikon FX lens (full-frame only), in addition to granting an extra stop of light. That means a 35mm f/1.4 lens that would otherwise be cropped to 50mm effectively becomes a 35mm f/1.0 lens on your E-mount APS-C camera. That's wild.
Metabones began taking pre-orders last week ($600), and early reviews with both photos and video show that there isn't much tradeoff in image quality when using the lens--corner sharpness only takes a small hit. Adam actually has one coming in for his own E-mount cameras, so we'll be shooting a video demonstration of the adapter in the near future.
If Metabones' system proves to be as good as it sounds on paper, it would make owning both a compact mirrorless system like Sony's NEX or Panasonic/Olympus' Micro 4/3rds (speed booster adapters for MFT coming later) much more viable as a companion camera to a high-end full-frame Canon or Nikon kit. That way, you can buy just the MILC body and invest in full-frame lenses for your DSLR.
Correction: fixed focal length explanation in first paragraph.