MessageBox is a plugin that overrides `Ext.MessageBox` class from core.
The idea is to provide equivalent native implementation when available.
But you should not have to rewrite a single line of code:
I've written a phonegap plugin that does exactly that for Phonegap!
There is a pull request ongoing so that it can join the official plugin repo.
You can find the sencha-touch plugin below :
Hope it helps,