You can connect a Xiaomi Mi Band 2 or 3 to the app if you enable the option "Use MiBand 2/3" in OTHER SETTINGS. You have to unpair the band from other apps like Mi Fit, or else it might not appear in the device list. After connecting (and pairing) the Mi Band you should put it in a homemade cardboard die diagonally.
Here is how you can make the die box with the Mi Band inside:
When the color die is ready and the Mi Band is connected, first you should calibrate the die.
Go to the Home screen of the app, and the logo should change to a question mark. Tap the question mark, and a color palette will pop up at the bottom of the screen. Now tap the color you se on TOP of the color die - the question mark should change into a circle filled with the selected color. When the color is set, turn the die to another side and tap the new color on top. Repeat this with each of the 6 colors, and the color die should be fully calibrated.
Here is a screen recording showing the connection and the calibration process:
The video below shows the calibration process from your view:
When the Mi Band color die is connected and calibrated, you are ready to use it with two of the routines: