Will the Apple Watch have enough precision in its location to be able to determine when you approach someone (suggestion #5 in the list)? GPS isn't nearly that precise, especially indoors or around tall buildings, which is why most people haven't done this yet and you see hardware like iBeacon for more precise location data.
The only reason we don't already have a few dozen apps that would do this on our phones already is because of the lack of precision.
The only reason we don't already have a few dozen apps that would do this on our phones already is because of the lack of precision.