Dignlab showed off their wall-mounted PC at Computex 2009.  It's a surface-mounted Mini-ITX based unit, which comes with a 7" touch screen.  I'm not sure what market they are targeting, as I can't see too many people installing one of these.

A VESA mounted Asus Eee Top would look much nicer, this product looks like a giant version of the old style Apple iPods.

More info & pictures can be found here.