"Google Glass has been the subject of many articles that have raised concerns about the obvious, and perhaps less obvious, privacy implications of a device that can be worn by an individual and used to film and record audio of other people," the letter reads.
"Fears of ubiquitous surveillance of individuals by other individuals, whether through such recordings or through other applications currently being developed, have been raised. Questions about Google's collection of such data and what it means in terms of Google's revamped privacy policy have also started to appear."
The letter also makes reference to Google's future stance on facial recognition (the company will reject such apps for now), and asks what it intends to do with the data it collects from Glass users.