The "Mix" reference in the URL links to the Office Mix application Microsoft fielded last year. Mix is an add-on to PowerPoint that is aimed largely, though not exclusively, at the education market. Office Mix turns PowerPoint presentations into interactive online lessons.
Snip isn't the first snipping tool from Microsoft. The company already offers a OneNote Clipper clipping tool. And the aforementioned Garage has been working on a tool called "OneClip" that it still has yet to unveil.
Across the company, Microsoft is seeking ways to enable users to interact with their PCs and devices beyond simple keyboard and mouse input. Microsoft Research's Project Oxford, for example, offers developers inside and outside the company a variety of speech, natural language and computer vision application programming interfaces for incorporation into apps.
I've asked Microsoft officials for more details on Snip, including when and whether it will be available cross-platform. No word back so far. In the interim, there's a Twitter account for Snip that might be worth following for more information.