Exploratory Smalltalk VM

This sounds interesting, but I have no idea what utility it has at present:

Spy is written in RPython, and can be translated with the PyPy toolchain as C executable, as Java native backend, and as .Net native backend. Spy is the collaborative effort of the Squeak-PyPy Sprint in Bern last autumn. Spy has been realized by the PyPy Team and the SCG Group in only one week.

Update: Michael Foord has some details about PyPy on his blog