This Article considers the Fourth Amendment implications of a study on a passive monitoring system where employees shared data from wearables, phone applications, and position beacons that provided private information such as weekend phone use, sleep patterns in the bedroom, and emotional states. The study’s authors hope to use the data collected to create a new system for objectively assessing employee performance that will replace the current system which is plagued by the inherent bias of self-reporting and peer-review and which is labor intensive and inefficient. The researchers were able to successfully link the data collected with the quality of worker performance. This technological advance raises the prospect of law enforcement gaining access to sensitive information from employers for use in criminal investigations. This Article analyzes the Fourth Amendment issues raised by police access to this new technology. Although the Supreme Court currently finds government collection of a comprehensive chronicle of a person’s life to constitute a Fourth Amendment search, widespread employee acceptance of mobile sensing could undermine any claim in having a reasonable expectation of privacy in such information. Additionally, employee tolerance of passive monitoring could make employer data available to the government through third party consent. When previously assessing employees’ privacy, the Court demonstrated a willingness to accept the needs of the employer and society as justification for limiting workers’ Fourth Amendment rights. Ultimately, then, Court precedent suggests that passive monitoring could erode Fourth Amendment rights in the long term.