Update: this adapter is now in production and is available for sale on eBay.
A group of Taiwanese camera-mount-modifying-enthusiasts created a M adapter for Sony NEX E-mount cameras with a build-in focus helicoid that could turn a Leica M lens into a macro lens. “The Helicoid” allows you to further close focus than your normal M mount lens could:
Several sample images taken with different lenses are available in the same thread – in one case they managed to get a 15mm 2.8 zm lens to focus on a subject literally inside the lens hood. The adapter is in pre-production stage and should be available for sell in June.