A list of TouchEvent types is here:
Here is a document from Apple about touch events:
And a list of events supported by the Safari browser:
I don't have an iPad, but I would love to know, if you could successfully use one of these events in this context.
Edit: For example, orientationchange looks promising. Type something, then change orientation.
Keyup is used here rather than keypress (which fires only once for each down-up event) since backspace won't fire keypress events, which is a nice thing to have in a live environment. But I can't think of any environment which would implement keypress and not keyup, or how one might work around not having key events at all.
I did, however, discover that if you alert in mobile Safari (in simulation and on my iPhone) on a backspace keydown, the keyup never gets through and it will happily erase everything before the cursor.