NaviCAD is the only iPhone/iPod Touch app that lets you navigate around Google Earth models (KMZ files which are compressed COLLADA files plus textures) in the Google 3D Warehouse.
11/20/09 Note: Apple has approved our latest update to NaviCAD. It is available immediately in the Apple App Store. NaviCAD now renders all Google Earth (KMZ) models uploaded to the Google 3D Warehouse that have been created in Google Earth, Building Maker, and SketchUp. Texture processing is now faster and transparencies in textures are now honored--for example, here is a screenshot of Kévin Girard's Eiffel in NaviCAD.