It has not taken me long to come across one of the minor shortcomings of Unity, the InputManager.
It is very simplistic and apparently it cannot be changed at runtime or at least not after the initial Unity provided options screen!
I think players of computer games should have some flexibility to customise their controls for a game and it should be easy to do even on the PC not just on Consoles. Not all games need this but first person shooters and similar, do, in my opinion.
Yes, Unity provides some customisation but it is not very user friendly.
I've started to write my own screens and am researching alternate input methods so that I can change this in my own, more user friendly, menus.
This is a list of some of the information, samples and assets I have found:
This is the sort of thing I want but I don't need everything: http://cinput2.weebly.com/index.html
The demo for CInput is useful for finding the Axes used by gamepads: http://cinput2.weebly.com/demo.html
This free project supports Ouya and others at the level I need: https://github.com/pbhogan/InControl
Edit 16 Dec 2014: A project with the same name is now on the Asset Store: https://www.assetstore.unity3d.com/en/#!/content/14695