There is a story in 'The Time' today about Surrey and Sussex Police using an HGV to see other drivers doing the normal stupid things and then despatching a following Police car to pull the driver over. This includes no seatbelts, doing make-up. watching TV and steering with their elbows whilst knitting! They can also see what other HGV drivers are up to. Making and eating food or drinks is quite popular!
I'm glad they dont have these up here. I don't know how I could show my face at work if I couldn't do my makeup on the commute.
As Exige says, they've been doing this for years. Watch out for plain white tractor units on the motorway, driving solo !! They use other types of vehicle too & may be liveried.