  The concern on human health is often overseen while wearable technologies
attract exploding interests. Mainly due to the extreme proximity or a direct
physical contact to the human skin, wearable communications devices are
acknowledged to cause higher levels of specific absorption rate (SAR) at the
skin surface. Unfortunately, so far, we have found no study encompassing all
the aspects that the general public needs to understand about wearable
technologies--i.e., the analytical and experimental backgrounds, and report of
SAR levels generated from commercial wearable devices. In this context, this
paper provides an extensive review on SAR from various commercial wearable
devices that are currently sold in the market, as well as the analytical
framework and the current measurement methodologies for standard compliance
tests. Moreover, considering the present interest in millimeter wave (mmW),
this paper sheds light on the SAR evaluated at 60 GHz and also compares the SAR
to that measured at 2.4 GHz. We expect that this paper will be of value in
informing the general public of the safety in using the currently sold wearable
devices, and in igniting further study of the exact biological consequences
from electromagnetic field (EMF) exposure due to wearable devices.
