yes, but you can't compare viability of health bands versus that of a fully functional wearable iPhone (or any smartphone or PDA). a health band only needs to have an accelerometer, low powered processor, small amount of storage and bluetooth chip. wearable pedometers have been around for a long time and it would seem that the only recent technological advance was integrating bluetooth and redesigning them to look more "futuristic" than the simple Casio style watch they used to be. With the type of wearables we are talking about now, you'd have to add in a much more powerful processor, more ram, considerably larger storage capacities, wifi card, a touchscreen that is big enough for people of all ages to read yet small enough to maintain a typical watch form factor, graphics card (more than likely included in whatever SOC they use), a battery capable of holding charge for no less than 12 functional hours, and possibly the most limiting in terms of form factor: some sort of I/O for charging and syncing. and even when we manage to squeeze all of this into a device that provides enough benefits to make its cost worthy of sales figures anywhere near that of iPhones and iPads, we are still left with a UI that is inherently difficult using only touch navigation. an adult finger is not exactly the most precise input device for such a small screen.
