The iPhone doesn't feature a physical keyboard, and likely never will. However, one group of people are looking into creating a clip-on keyboard, which users could attach to their smart phone just like a Smart Cover. The accessory, called a "SmartKeyboard," is little more than a concept. However, as TUAW notes, it has potential.
The popular, free application for Apple's second generation iPad, Evernote Peek, has recently received an update. Now, users of the app can enjoy hearing audio clues, and interacting with study notebooks that have been shared with others.