Interval training is an excellent way to fit in an effective, fat-burning workout in a short amount of time, which is even more important when you're on vacation. If you'd rather not sweat all over your phone while trying to track your intervals, check out the GYMBOSS interval timer.
This compact, sweat-proof timer easily clips onto your clothes and stays put, even during plyometric moves. It also offers pre-programmed options for exact interval length and rounds complete with vibrating or alarm notifications. It's especially helpful with Tabata training sessions, when work/rest periods are shorter (but super intense!).