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There is a photoshop express for Android
https://play.google.com/store/apps/details?id=com.adobe.psmobile&hl=en

As mentioned Wacom has pretty much cemented their name. a friend has a pen a touch display - set her back around $2700 - its like drawing on a screen, she uses mostly adobe products. I got to play...

honestly the screen/tablets are the best - but NOT cheap