Just figured I'd post here a couple of issues with footbot sensors I had and have since got figured out, in case anyone else is having them.
I found this on the github page, but could not get argos to recognize it. Carlo advised to just use the generic differential_steering sensor, as it is the same.
I was having trouble getting reading from this. I fixed it by doing the following.
1) Add the corresponding actuator (even if you are not planning on turning the scanner)
2) Call Enable() on the actuator in the controllers Reset(). (When I had Enable() in the controllers Init(), the sensor was still not working)