iPhone Mobile Safari: Force keyboard open

Question

This is an HTML / CSS / JS (jQuery) iPad app. I've got a button, that slides down an input form. I'd like to focus the user on the input, and then launch the keyboard.

This is what I'm working with, but doesn't work:

$('#myFormField').focus();

This does indeed focus the input, but fails to launch the keyboard. Is it just not possible (for security reasons or whatever)?

Is there a way to force or simulate a user tapping the input (or anything for that matter)?

Thanks!