Sworkit lets you choose length and type of workout. The only thing I don't like is the 30 second breaks it gives you every 2 to 2.5 minutes. I wish I could turn that off or make it less. Especially when I'm doing yoga, I don't need a break.
The pro version is only $.99. What I like about Sworkit Pro is it will announce each workout so you don't have to look at your phone the whole time and it has how to videos during workouts. Sometime I'm not quite sure what a workout is based off the name.
Now if only I remember to do it at night even just for 5 or 10 minutes!