iOS/Android: Sworkit is one of the better exercise apps out there because it's free, simple to use, and has a lot of options. An update today brings in a whole new design, and some new workouts.
The big change here is the new design, which makes browsing different workouts a lot more intuitive. Beyond that, there's also a new "five minute workout" option alongside a couple of new general workouts. As always, you can still create custom workouts or just randomise based on the amount of time you have, so it's a great way to fit in a workout when you don't have a lot of time.
Sworkit (Free) [iTunes App Store]
Sworkit (Free) [Google Play]