Motorola Atrix, Ubuntu Phone, Windows Phone 10 has Continuum. It's been tried before.
I have a windows phone with continuum and tried it, and while it is executed quite well, it wasn't very useful due to the lack of apps. You can use any windows 10 device as a screen/keyboard/mouse, but usually the laptops I have near me are mine, so they already have everything I need. If it had an ability to carry a self-contained programming environment I might have played around with it more.
It does make a fine fallback presenting device. You put your powerpoint slides on the phone, and if all else fails you can project your slides to any w10 laptop that's near.