My first QC 3.0 Plug-in. (Note this is only compatible with the Quartz Composer found on the Leopard developers install.) This Plug-In uses a public domain KLT feature tracker to attempt to track N features between the two input images. It assumes the inputs are from the same video input stream. It could be a lot more efficient, but it's my first try. Full source included.
My second QC 3.0 Plug-in. (Note this is only compatible with the Quartz Composer found on the Leopard developers install.) This Plug-In takes in a structure such as that outputted by FeatureSelector and plots little dots on the input image at their locations. Full source included.