Ekahau Wi-Fi T301W Wristband is a wristband can know the location of someone using Wi-Fi signals and this may be the first in the world should be. This wristband has the same function as finder GPS products that we often discussed but this diffrent because using Wi-Fi signals as media. It features a very useful tool to track someone in the building not covered by GPS. And regarding the accuracy of a given location, Ekahau is quite accurate T301W is the error rate only a few feet.

Source