Yes, I'd really like to be able to run with just a small device while still getting the basic updates. I'm a jogger and my partner prefers cycling, meaning if we go out to exercise together, she's a few kilometers away from wherever I am at any given time, so coordinating finishing up her hour of cycling and my hour of running can be a chore.
I really don't like carrying around a large 5.5" screen phone while running; the armband pouches are about as convenient as you can get and I appreciate them for what they are, but just having a small watch device would be far better for me (and for many I assume). Easier to waterproof so I don't have to worry about it when it rains, less to break should an accident happen (I trip, collision with cyclist, etc), lighter overall. That plus having a means of shooting off a quick message via Siri or whatever voice service to just keep track of people would be wonderful.
Do I need it? No, but boy do I want it.