The next version of the Switchr app will give you the opportunity to have multiple sets of buttons. To switch between these profiles this is one of the controls I have in mind.
Get a bigger version at: http://colibri-interactive.com/dribbble/switchrapp_profile_full.jpg
The app is available at the Apple app store and at http://switchrapp.com (just in case you're interested ;) )
keyboard shortcuts: ← previous shot → next shot L or F like Z toggle zoom