It must be a failure of my imagination, but I don't see a smart watch (in the next couple years) being both attractive to the general consumer and solving the same problems as the FuelBand does. That's partly because I can't imagine what features would make me want to buy an iWatch. So I expect that Nike's going to be forced to compromise functionality to fit the limited capabilities of general-purpose devices.
For example, Craig's proposed iRing doesn't even mention tracking motion activity: http://furbo.org/2014/03/13/wearing-apple/
Also, maybe it's the specific app I use, but using the M7 kills battery life on my 5S.