Some of the things I miss in XRP are:
- Display for showing messages to user
- more user buttons (and easier to reach, too)
- Larger and easier to reach on/off switch (whne the robot misbehaves, you do not want to be squinting in search of the switch).
So, I made an add-on board that has all that (and, in addition, a couple of Neopixels).
All design files and software are available in github, and the whole project is documented at