I finally tried CozyBlanket and I REALLY like it!
They just updated it to include UV & baking — incredible for an iPad app. I had sticker shock when it first came out: $90 is not cheap* for a specialist tablet app that only does retopology (+ had issues at launch). But with all of these features, it's worth it.
Haven't tried UV or baking yet, only retopo on their default frog (pic 1). Works well.
You can do basic retopo, UV, & baking with the $20 Lite version (pic 2). I think it'd be perfectly fine for things like a head or small prop; like this frog or simpler.
More complex models would be frustrating without the $90 features. On the comparison screen, you can scroll down the full list, tap on each for a visual & explanation of what it does. (pic 3)
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The tutorial doesn't show some key features:
The constant double-tapping to move points or edges was annoying: You can get around this with the side buttons, like Tweak:
Those are Press & Hold.
You can draw entire rows: draw a connecting rectangle to the row you want to add to.
Problems so far: (pic 4)
If you try to move an open row of edges, the polys can get "stuck" and only shorten. (See screenshot: right-most row is shorter.) To move those edges out (elongate), you have to tweak individual points.
You have to zoom in close to tweak a row, else it won't recognize it & picks up a point instead.
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Other software I've tried retopo in: Zbrush (ZRemesher, ZModeler & Topology brushes), Blender (no addon), C4D, 3DCoat, Topogun (trial).
I won't go into detail about each, but CozyBlanket was instantly easier, more intuitive, and pleasant than any of them. Eliminating frustration is worth a lot.
Topogun is a close 2nd; 1st in some ways (here's a good thread about it). But it's $100 for retopo only and the developer seems MIA. So CB looks like the better deal if you have an iPad.
The 3rd option I'd try is Retopoflow in Blender. It's popular, actively being developed, and there's talk it'll be integrated into Blender main.
