We are in a motorhome. Our cat hides under the recliner/sofa when we are traveling and no doubt sleeping. When we park she hops up on the dash and will lay there for hours just watching what is going on outside.
If you are in a trailer or camper I would suggest having some kind of shelf or area where your cat can lie down and look out a window. They seem to be very content doing that.
We do put our cat on a harness and leash occasionally and take her for short walks, but she is usually happy just being able to look out the window.