Oh, that's nice! I've had Dash for a couple of years now and love it, but it would be very nice to have it open on my iPad while I develop on my mac! Awesome!
[0] http://zealdocs.org/ [1] http://dash-port.launchrock.com/
[0] - http://kivy.org
BTW, Zeal's original author here - thanks for mentioning Zeal and good luck with your project!
As some personal advice, I wouldn't try Kivy for such content-oriented desktop app. I've tried briefly using it once for doing a very simple application, but it seemed much harder to implement usual desktop-like widgets. Overall it looks like it's good for graphics-rich and custom-rendered applications.
You'll also need some HTML rendering engine for docsets. While there are Kivy projects like https://github.com/kivy-garden/garden.cefpython or https://github.com/kivy/kivy-berkelium aiming to provide exactly that, they don't seem very mature.
However, I don't claim to be Kivy expert at all, and maybe you'll have good experience with it.