Mobile users will use touch events instead of click events and likely your interface will be different and the screen width will be different. Check for these things along with keywords from the user agent string to determine mobile users from other users.
Return key on a control in a form will fire a submit event. Check for cursor position in your submit handler.
Are you saying block form submission unless the cursor is over the event target?
If so:
* How to handle legitimate requests from mobile users?
* How to handle form submissions with the "return" key?