GhostDoc is described as 'Simplify your XML Comments! GhostDoc is a Visual Studio extension that automatically generates XML documentation comments for methods and properties based on their type, parameters, name, and other contextual information' and is an app in the Development category. There are three alternatives to GhostDoc for Linux, Windows, BSD, Haiku and Mac. The best alternative is Doxygen, which is both free and Open Source. Other great apps like GhostDoc are LuaDoc (Free, Open Source) and LDoc (Free, Open Source).
Doxygen is a tool for generating documentation from annotated C++ sources, as well as other popular programming languages like C, Objective-C, C#, PHP, Java, Python, IDL (CORBA, Microsoft, and UNO/OpenOffice flavors), Fortran, VHDL, Tcl, and to some extent D.
LuaDoc is a documentation generator tool for Lua source code. It parses the declarations and documentation comments in a set of Lua source files and produces a set of XHTML pages describing the commented declarations and functions.