Both AForge.NET and Accord.NET make extensive use of unsafe code. This feature has not been officially available for Windows Phone 8, but by manually editing the project file of the Portable Class Libraries in question, I have been able to successfully circumvent this limitation.
After upgrading to Visual Studio 2013 Update 2 last week, it seems like this loophole of mine is now at least detected. When trying to compile the libraries containing unsafe code, I get error messages like the following:
Error 1 'Allow unsafe code' is not supported by one or more of the project's targets. [...]\accord\Sources\Accord.Math\Portable.Accord.Math.csproj 0 0 Portable.Accord.Math
For some reason, the libraries still appear to be successfully built, but I am currently not sure of their applicability. Further testing is obviously necessary.
Note: no error is reported when I build the libraries using Visual Studio 2012. For my own peace of mind, maybe I should revert to the previous VS version, then...