My solution - not fully executed yet, though - to this problem is to have multiple monitors, keyboards and trackballs in my working room at home. The primary place I'd work at is a standing desk, with keyboard, trackball, monitor perfectly set up for this purpose. Beside these, there is another monitor, another keyboard, and another trackball, at a lower level, set up for when I'm sitting. The screen is mirrored on both.
I can walk around if I want to, because I have screens on the side too - though not input devices. I'm ok with inputting in two possible locations. But it is useful to be able to turn around, stare out the window, then look aside, and see my screen.
There is also the TV in the living room, when I go out and explain stuff to my wife (rubber duck programming is awesome). There, I use a laser pointer to point at specific parts of the screen. If I wanted to, I could have a small device, like the raspberry pi in that room, with other input devices attached, if I'd need to do anything there. The raspberry would just proxy the input events to my main computer over the LAN (there are N number of solutions on how this can be easily done).
I tried experimenting with other ways of working with a computer, such as speech recognition, but found that to be lacking at this time. Takes far too much time to set up, and the reliability is low. I'm also playing with Stenography, where I press chords to input text, instead of typing it out by the letter: this drastically reduces hand movement, and increases your speed, but the learning curve is steep, and takes a looong time. And it still requires a keyboard. Or a piano. A piano may even be better, dunno, didn't try that yet.