Steve Demeter's Demiforce software is showing off "Trism," a Bewjewelled-family match-three game that uses triangular pieces that fall based on the orientation of your iPhone. The pieces always slide down towards the ground as if they were affected by real-world gravity.
Game Set Watch has an interview with Demeter where he talks about his company's history, the inspiration for the game, and his mad dash to try to find out everything he can about the upcoming iPhone/Touch SDK announcements next week. Understandably so—the first stand-out puzzle game for the iPhone to be available for sale on iTunes should bring in a fat stack of cash for its developer.
I started by making an Excel spreadsheet, listing all the different kinds of game input methods available, such as directional, directional + buttons, directional + buttons + mouse, and mouse only. Then, I listed the natural endpoints of evolution for games for each control mechanism.
For example, Tetris I feel is a natural endpoint of directional-only gaming because it uses the keyboard's functionality efficiently and to its fullest extent. The 2D sidescroller is a natural endpoint of directional + button gameplay, adding the concept of multitasking to the mix. FPSs are natural endpoints of keyboard and mouse gaming, and games like minesweeper and solitaire are natural endpoints for mouse-only gameplay.