I want to measure and log the actual speed (both linear and angular) of each footbot throughout a simulation run. Note that I'm looking for the actual speed as known to the physics engine: if the footbot is already collided with a wall and attempts to drive "into" the wall, it looks like the differential_steering_sensor would report whatever attempted velocity was sent to the differential_steering_actuator.
Now I've fully jumped into the deep-end of trying to understand the chipmunk-physics engine.
What's the sane way for me to measure the actual speed of the footbot?