Aza Raskin proposes a new home button for iOS:
Camera shutter buttons have a two-stop action. Half-press them to lock focus and aperture settings, fully press them to take the picture. There’s a delightful tactile indent at the half-way mark so that your fingers know what’s going on. Let’s borrow this two-stop action for the home button. Press half-way to go to the app’s main screen, all the way to go to the phone’s main screen. If you need to fully escape mash the button. If you just want to head back to the main-screen of the app, tap lightly.
Interesting idea — I wonder how to make such a button that would not be constantly pressed in your pocket.