  The Google Glass is a mobile device designed to be worn as eyeglasses. This
form factor enables new usage possibilities, such as hands-free video chats and
instant web search. However, its shape also hampers its potential: (1) battery
size, and therefore lifetime, is limited by a need for the device to be
lightweight, and (2) high-power processing leads to significant heat, which
should be limited, due to the Glass' compact form factor and close proximity to
the user's skin. We use the Glass in a case study of the power and thermal
characteristics of optical head-mounted display devices. We share insights and
implications to limit power consumption to increase the safety and utility of
head-mounted devices.

Human-Computer Interaction