I have been looking for something like this rather than the more free form graphical mind mapping software. Just bought it, for $1.99 from the Google Play Store and there is a free version, and although some of the reviews suggested it had kind of a steep learning curve so far I've found it to be pretty straightforward. I haven't really explored some of its more powerful features yet but so far I am extremely happy with it.

Sent from my Galaxy Note 10.1

Sent from my Galaxy Note 10.1