This is an interesting question, and something I've been thinking about because I'll be gone throughout the month of September -- and may not have a way to play videos or DVD's -- not many hotels have DVD or video players in their rooms.
So, I've been puzzling over this, too, mostly because I don't push myself as hard as Cathe does.x(
But I've come to the conclusion that I have to continue to exercise intensively even while I'm gone -- mostly because an entire month would just be too much to be gone from exercise.
There's a book -- I recommend this book all the time -- READY, SET, GO by Phil Campbell and he has some recommendations for intense exercise -- but outside -- I think what I'm going to do is review that book and bring it with me and just do what he recommends. One can always sprint for intensity, I suppose, and cardio is easy, one can do plyometrics (jumps) pretty easily too, I guess. Probably the hardest thing will be the weights and strength workouts, cause while I might push myself cardio wise, I don't tend to on strength exercises...
Well, there's probably not going to be anything for it but to take some weights with me, it appears -- probably light weights that I can double up.
I know this didn't answer your question, but thought I'd let you know I've thinking along similar lines, as well.
Have a good one.:7