Quite a few customers have SharePoint 2013 developer environments that do not have access to internet. That poses no problem to install Visual Studio 2012, but installing the Microsoft Office Developer Tools requires internet access as it makes use of the Web Platform Installer. But, appearantly Web Platform Installer has an offline mode:
The article shows the commandline options to create an offline cache. Either for all products (not recommended) or a specific product, which is the Microsoft Office Developer Tools for Visual Studio 2012 in our case. A big thank you to Mauricio Ordonez for sharing this.