This document describes techniques and systems that enable a smartphone-based radar system for facilitating awareness of user presence and orientation. The techniques and systems use a radar field to accurately determine a user's location and physical orientation with respect to an electronic device, such as a smartphone. The radar field also enables the device to receive 3D gestures from the user to interact with the device. The techniques allow the device to provide functionality based on the user's presence and orientation, and to appropriately adjust the timing, content, and format of the device's interactions with the user.