1) An innovation is the introduction of something new. It can be big or small, brand new or a little different. It can be clearly complex or seemingly simple. Innovations are often thought of in terms of technical achievement, but can also be a design.
What is not innovation is invention. An inventor discovers the "next big thing," but is unable to find anyone to produce it. For this invention to become an innovation, a public needs to be introduced to the invention and have said invention improve their lives in some way.
I think that the piano stairs is the best innovation idea while the worst is the hat that allows you to stick your head to the wall when you want to sleep.
I think its a useful innovation as it has a multi-touch interface. It uses fast 3G and Wi-Fi device and has thousand of amazing applications. It also uses a software based keyboard and responds to motion such as turning/tilting.