Motion sensors, CO2 sensors and the like are considered to be benign forms of monitoring, since they don’t capture images or personal data about us as we move through the buildings we visit. Or at least, that’s what we want to believe. Guest blogger Professor Matthew Chalmers (University of Glasgow) helped develop a mobile game called About Us as part of the CDBB funded Project Oak. The game takes players through a mission using information from building sensors to help them achieve their aims — with a twist at the end. He writes about why we all need to engage with the ethics of data collection in smart built environments.