You see the word 'Typing' in place of the contact name at the top of the screen in the PingChat! app. I think it will be similar to that. When you consider all of the processes that are occurring on the iPhone while it's turned on and in use as well as the power it takes to display everything that's on the screen, displaying 'Typing' instead of 'Name' is inconsequential. When you consider all of these processes, I'm guessing that this added feature will cause less than one second more of battery consumption per charge cycle.