ViewUp (http://viewup.info/) is a great program to use for viewing SketchUp files on smartphones and tablets (Apple iOS and Google Android). It's free and available in the platform appstores by searching on ViewUp.
I work quite a bit in Sketchup planning layouts and building details of my cabin. I've been looking for a decent viewer for tablets and smartphones that I could use to show in-progress models to friends and associated when I'm not sitting at my desktop computer with a copy of Sketchup running. In the past, I always had to export 2D (picture) files of certain views in order to display them on my devices. Sketchup has offered a fairly expensive ($9) app that doesn't get good reviews.
ViewUp works quite nicely. And it appears to support several different file formats for other 3D applications. It allows me to do complete walkthroughs with fairly intuitive touch gestures. I use onedrive to store my Sketchup files, and I can access them directly from my iPad mini to get the latest version. Makes for a very nice tool stack for those who use Sketchup.