Ubicomp paper on a study of indoor bluetooth propagation using the Active Bat system. This work with Alastair Tse used ultrasonic location tracking to conduct fine-grained Bluetooth signal strength surveys, giving us unprecedented accuracy in mapping radio propagation indoors. We discovered that Bluetooth is actually poorly suited for fine-grained location inference due to hardware and specification limitations, and that device movement speed significantly impacts available bandwidth. The study provided valuable data sets for the research community and practical insights about the limitations of using Bluetooth for ubiquitous computing applications.