This now supported in VS 2012!
Previously, XML tags in the comments were only read in by C++/CLI, not plain old C++.
VS 2012 now brings at least some of this into regular C++ – it is in the What’s New in Visual Studio 2012 and in the MSDN docs: XML Documentation (Visual C++).
I’ve tested it with my own application in 2012 ultimate, and I can confirm that the summary, para, and seealso tags are all pulled out an formatted for tooltips.