It would be helpful to have a node that does the reverse of the kinematics node for the purposes of simulation and verification. The node would:

1. Subscribe to the /drive/motors topic
2. Based on independent measurments and understanding of the robot physics compute the estimated direction of travel.
3. Publish a Twist message that announces the calculated travel direction.

It's important that this node make calculations independenlty from the code in the kinematics node because it will be used for verification purposes. Possible future work could also compare the ouptut of this node to measured accelerations from the IMU.

This is a good project for an intermeidate programmer. Work on it will not be in the critical path so you can take some time to figure out all the issues.