I don’t have much personal experience here but I’ll share what I’ve heard from others. Lots of positive talk about the iPad Pro and Apple Pencil. Our very own @webmaid loves it, Mike Rohde has been enjoying it (review here: https://medium.com/@rohdesign/impressions-of-the-9-7-ipad-pro-apple-pencil-1567b1952434#.phc55hhvn) – sorry about the ugly link – and I’ve heard other positive things here and there.
The two apps that I hear referenced most are FiftyThree’s Paper and Autodesk Sketchbook.
Per @melainedcruze‘s comment above, sounds like the Galaxy Note is a great option as well.
Hope that gives you a place to start – would love to hear the personal preferences/suggestions of others!