We have featured many practical mini Bluetooth keyboards for iPhone and other smartphones, but if you want an integrated solution, the concept iPhone 4 keyboard case should be able to give you some inspiration.
The Fliptype is a practical design concept by NOS, a Mexico based design studio, and designed to offer you an comfortably and tactilely typing experience on your iPhone 4. As we can see from the images, the iPhone 4 case features an integrated flippable typing strap which can perfectly cover on the virtual keyboard of your iPhone 4, and allowing you to type via its tactile keys. When not in the use, the keyboard strap can be tucked away at the back of the protective case for portability. After the break, check out the demo video and images of the design concept.
Additionally, if you want similar, available options, you might like to check Spike iPhone 4 case.
Source: Yanko Design