Don't have a gym at your hotel and you want some exercise? When driving, stop at a rest stop and use a bench for step ups or push ups. Be sure to stop often when driving to stretch your legs.
If your flight is a long one, get up and walk around. When seated for a long period of time rotate your ankles, first one way and then the other way. Take off your shoes to allow better circulation. I always take a pair of socks just for long flights.
In your hotel room, do some squats or lunges while watching TV. Take the stairs if you can. And always include a walking tour of the city. Great exercise, great photo ops and great exercise.