Hi, I use Artrage as it's is one of the best handpainting apps out there and has full psd output/input . I use it for everything. CA4 'almost' already supports it but doesn't have the realtime hook up as i can see in your demo with the other apps (photoshop etc).
It would be super amazing if CA4 supported Artrage directly because at the moment I need to send from artrage to photoshop then back to CA4 which defeats the whole point of the pipeline feature really.
It already seems quite close (PSD import/export already works) so I would hope it wouldn't be a huge amount of work for you but this for me would be a lifesaving feature..and I would think many other too.