  As we await a vaccine, social-distancing via efficient contact tracing has
emerged as the primary health strategy to dampen the spread of COVID-19. To
enable efficient digital contact tracing, we present a novel system to estimate
pair-wise individual proximity, via a joint model of Bluetooth Low Energy (BLE)
signals with other on-device sensors (accelerometer, magnetometer, gyroscope).
We explore multiple ways of interpreting the sensor data stream (time-series,
histogram, etc) and use several statistical and deep learning methods to learn
representations for sensing proximity. We report the normalized Decision Cost
Function (nDCF) metric and analyze the differential impact of the various input
signals, as well as discuss various challenges associated with this task.
