When plugged in the OBD-II port, and HUDWAY Cast not connected to a smartphone, the speed and RPM are fetched to HUDWAY Cast. When HUDWAY Cast is connected to a smartphone, the smartphone screen will be mirrored to HUD.
ATTENTION:Oh hybrid vehicles, OBD-II connection may work incorrectly, and only get the data and power when the vehicle is using its combustible engine. When working off electrical motor, the power supply to the OBD-II port may be insufficient to power the device.
See the video on connection options and what you will see on HUD when connected to an OBD-II port: