I found a great video on touch user interfaces (or TUI’s). It took place at NYC IxDA and the speaker is Dan Saffer, who is the author of Designing for Interaction: Creating Smart Applications and Clever Devices.

Some key notes that I took from this video are as follows:

• 1. Avoid putting essential features or information like a label below an interface element that can be touched, as it may become hidden by the user’s own hand.
• 2. Aim to have targets at least 11mm big. The iphone’s keyboard gets away with less by using adaptive targets that become bigger when the program and predict the next letter to by typed.
• 3. The more complicated the gesture, the fewer people who will be able to perform it. The complexity of the gesture should match the complexity of the task. The best, most natural design, then, are those that match the behavior of the system to the gesture humans might already do to enable that behavior.

I was also able to find the slides for this presentation. They are located here.