I cloned git://github.com/xamarin/XobotOS.git and followed instructions from https://github.com/xamarin/XobotOS/blob/master/sharpen/README
Apparently mono's team has pre built version which readme instructions are related since adding provided site directory does not adds sharpen plugin to available in "Install new software" dialog in eclipse. I guess it has to be built.
So how to build this eclipse plugin? It does not seem to have any ant/maven files.
You have to use Eclipse 3.4 http://www.eclipse.org/downloads/packages/eclipse-classic-342/ganymedesr2
However I have errors in source.