Multitasking not only can kill your productivity, but if you're trying to do it at the wrong time - while driving, for instance - then it can just plain kill you.  How many people reading this have tried to briefly answer a call while driving, or reply to a text?  Product development consultants Kaleidoscope have come up with a way to handle those interruptions, and rather fittingly they've called it Tame.  A Bluetooth-enabled cube, Tame has a number of status messages which can be selected simply by turning the cube to whichever face is most appropriate.  In the car?  Turn it to say "Call you back later... I'm driving."

What's clever about the concept is that Tame would connect not only with your iPhone but with your email, IM client and more: 

"Currently, multitasking requires people to manage multiple devices and applications independently. An away message in Instant Messenger is useless to a person who is making contact via mobile phone. Tame delivers convergence of all these services, ensuring that someone trying to contact you will know your status regardless of the method. Online software allows the user to customize their status messages from anywhere they have internet access, and Tame updates live via Bluetooth" Kaleidoscope 

Of course, it's just a concept right now, but it's one that could quite readily be developed as a real product I think.