On the PDA or tablet there would be an eight way centred joystick under Bob's left thumb. Pressing the joystick would step the focus through the four permanent panels. Pressing and holding would step the focused panel through normal, larger and full screen. Nudging the joystick left or right would tab through items or options in the panel and nudging up or down would either scroll through the view of a panel or change the value of tabbed options.
On the desktop the screen edges could be activated to replicate the joystick; slamming the pointer against any edge would simulate nudging the joystick and a mouse button under the thumb would simulate pressing the joystick.
Screen corners could be used for quick jumping. An open document could be slammed top left for later reading; an item or clip could be slammed top right to the temporary stash; contacts could be slammed bottom left to add to the speed dialling list; bottom right could be a screensaver or hardware status display.