Cinder recently introduced a new API that allows you to use the same code on Windows 7, the iPad and the iPhone for multiTouch. This code demos a current branch which allows you to use the MacBook trackpad as a multiTouch device with the same API.
The video shows our msaFluidMultiTouch sample (which ships with Cinder version 0.8.1) running on a (not very recent) MacBook Pro with no modifications to its source. The same demo runs on Windows 7 multiTouch devices as well as the iPad. It is based on the Cinder port of Memo's excellent MSAFluid (http://www.msavisuals.com/msafluid) library. The MacBook Pro trackpad is able to track at least 10 simultaneous touchpoints, and its accuracy is quite impressive.