If I had it my way, I would carry around one device that served as every device I use, phone, watch, tablet, and computer.
The device would be the size if the old iPhones so it is easy to carry around. It would have a computer sized hard drive, at least 500gb, a great camera, and be very fast.
The main screen I would interact with though would be built into my eye-glasses, but not in some weird Google glass way. Think of it more like heads up display in a car.
What I see in my glasses would change depending on my situation. For most situations, it would show basic items like time and any reminder I needed. These would show up out of the way in the peripherals of my view.
If I needed to pull up an app, I could do so by looking at an icon in one of the corners, and a sort of app drawer would pull up. The device would detect which app I am looking at and open it.
Each app would be display differently depending on the situation, so some would be out of the way, while others would consume my entire view.
At the office, my device would connect to a wireless keyboard and mouse (or the device could serve as a trackpad of sorts), and the display would cover my view similar to looking at a monitor.
The view becomes more of a computer type interface, however you can organize each application window spatially where some application windows would appear farther away than others.
For meetings, a presenter could display the screen they are looking at to the glasses of other people in the room (or who are meeting virtually).
In video chat, the other person would appear as more of a hologram that flat image on a screen.
Sound would be delivered through a small set of wireless earbuds that tuck away out of site.
While driving, riding bikes, etc., the device would detect what I was doing and remove all distractions. For example, it could see that I was driving, so it would take away notifications, and not allow apps to launch while displaying navigation, speed limit, and warnings about driving conditions.
Finally, the device, glasses, earbuds, keyboard, etc all charge wirelessly through the air so you never have to connect anything to a charger ever.