We live our lives across channels.
It's common to see someone using a smartphone while sitting in front of a computer screen, or reading a magazine while watching TV.
As users, our context is the situation we're in, including where we are, what we're trying to do, how we're feeling, and anything else that shapes our experience. Our context is always unique to us and can't be relied upon to hold steady.
In this context, I'm using several different channels: Twitter, a smartphone, and TV.