Eh? AFAIK, Accelerate.framework doesn't do anything with the GPU -- its "just" a set of highly optimized functions for math/DSP/image processing operations.
vImage is not GPU accelerated and provides no useful operations for decoding video. You may be thinking of OpenCL, which also provides no useful operations for decoding video, or VideoDecodeAcceleration, which is already supported by QuickTime and needs no further 3rd party support.
