And why, you might ask? For one because i made it :)
But seriously, if you are into intense, repetition-based training, you might want to take a look at it. It's an [iOS app](https://itunes.apple.com/us/app/training-time!/id692787267?mt=8) that allows you to set the duration of each repetition, as well as the resting time between reps. Then all you have to do is hit start and listen to the app as it tells you when to rest and when to exercise.
Because i rarely develop something i don't want for myself, i've been using it for a while, along with a set of 5-6 different exercices, for a total of 7-8 minutes of training everyday and i've found it to be a nice and fast way to be in good general shape. Your mileage may vary but you can always top that with, who knows, a bit of [Kung Fu](https://en.wikipedia.org/wiki/Wong_Shun_Leung) ;)
Training Time! can be found on the App Store, [here](https://itunes.apple.com/us/app/training-time!/id692787267?mt=8).