Nice. If you add some camera to the leds, using Aruco markers you can easily get the camera pose and adjust the led colors accordingly to draw a predefined image without needing a steady hand.
You probably can turn this into a phone light brush app if you use front camera and screen as a led (the torch usually don't change color), but it still has some challenges with respect to latency (in dark environment cheap camera get slow) and user-friendliness specially if it needs calibration.
As I mentioned latency is indeed an issue, but I don't think it matter that much. Your pixel will be offset by the movement during this 50ms (probably more) which will be a typically a few centimeters, so edges will get a little blurry but I'm not a light painter expert.
If it is really a problem, assume pose velocity from the previous frame positions and correct for latency and turn off the screen if acceleration sensor is greater than a value.
That's true, if you have a phone you can use the sensors on it to do dead reckoning in the interim. I'm not a mocap expert, but this seems very doable! It would be a great idea.
You probably can turn this into a phone light brush app if you use front camera and screen as a led (the torch usually don't change color), but it still has some challenges with respect to latency (in dark environment cheap camera get slow) and user-friendliness specially if it needs calibration.