Hi,
Is it possible to get the current speed of the nozzle head, in all 3 directions, through a plugin?
Communication with the printer is not real-time in that way. The current speed of the printer varies massively depending on where it is in the move, what the next move is etc. The acceleration and jerk parameters will have an influence making the speed a curve rather than linear.
It would be possible to track the feedrate sent to the printer from a plugin, but you won't know exactly when that move is executed. A user can also set the feedrate modifier on the printer, which would then throw out any calculations you are doing.
The question is how exact should be the result. A GCODEs feedrate calculation e.g. after sent to printer can be done very easily.