The Enterprise edition of GhostDoc includes command line utility that enables continuous integration to generate help documentation as part of the build process.
If you don't have GhostDoc Enterprise installed, you can download the free 14 day evaluation copy here.
The GhostDoc Enterprise command line is quite straightforward to use. Here is a quick reference:
solution file to load (*.sln file)
help configuration to use
show detailed console output (brief is default)
hide console output
helpConfiguration - is the configuration you save in the Build Help File dialog
projectConfiguration - is your VS project/build configuration - Debug, Release or your custom config.
SubMain.GhostDoc.Cmd.exe /solution:"Sample.sln" /helpConfiguration:"HelpFile" /projectconfiguration:"Debug" /consoledetailed