«Xiaomi's Mi Mix 2 is the most luxurious Chinese phone ever made... [and] uses ultrasonic proximity sensors in lieu of those ugly black dots.» (ellipticlabs.com)
The phone sports a ceramic build with a hidden ultrasonic proximity sensor. (techandroids.com)
Other than that, the front is all screen, ultrasonic proximity sensor embedded directly into it, and something called «cantilever piezoelectric ceramic acoustic technology» replacing the conventional earpiece speaker. (pocketnow.com)