> At the point you're carrying around a keyboard anyway, why not just have a Macbook Air?

Because you _don't have to_ carry around a keyboard and a display if you don't plan on producing content and just want to make phone calls read ebooks.

Can I tear off the screen and keyboard off a Macbook Air and use it as a phone? No? Well then I want a Ubuntu Phone then.

Well at least in theory ...

Another way to look at it, I already have a TV, a laptop, a tablet, and a phone. As mobile hardware gets faster and better, I would eventually just love to have one device -- a phone. I could connect it to my large screen tv, a good keyboard, a smaller LCD display, USB storage and so on.

I thought it would be great to have one device as well, but then I realized that sometimes I want to use my phone while watching TV or using the laptop, so they can't really be one device, unless I wear a wireless headset, which I don't really want to carry around along with my phone (another thing to charge, another thing to lose).

A multi tasking OS with a powerful CPU and wireless video streaming should provide those at least in theory. There is actually Miracast http://en.wikipedia.org/wiki/Miracast so in theory the bits and pieces are here already they just have to work as a package.