This letter, submitted for the record to the House Oversight Committee’s Information Technology Subcommittee hearing on “Examining Law Enforcement Use of Cell Phone Tracking Devices,” calls on Congress to pass legislation, beginning with the GPS Act, which would impose a warrant requirement and other protections for any device that collects location, device, or content information. The letter also urges the Executive Branch to (1) issue comprehensive guidance requiring federal agencies to obtain a warrant and adopt other privacy protections when using current or future technologies that collect location, device or content information, and (2) strengthen the current DOJ guidance on Stingrays to eliminate loopholes to the warrant requirement, provide notification to individuals whose information is collected by the devices, require states and localities to adhere to privacy protections, further restrict retention of information, and increase transparency.