I have been doing a lot of running and cycling Tabatas recently and my speed has vastly improved. This app makes Tabatas so much better because I can just follow the prompts and not think about it. I use a set of bluetooth headphones (Plantronics BackBeat FIT-- awesome for exercise) and follow the voice prompts. I also love how the app can start/stop selected playlists to play in the background so I can take my mind off how much pain Im in. But two features are needed. First, the app needs to announce audibly what interval I am doing. For instance, it should announce "interval 1," "interval 2," etc. Tabatas are so hard and knowing which interval Im on makes it much easier. Realistically, the voice prompts probably dont have to count beyond 10 or 15-- anyone doing that many Tabatas should probably be breaking them up into multiple sets. Second, there should be an option to turn off or change the preparation time on the first Tabata set. I use the preparation time feature as a way to control my recovery after finishing one set and starting another. Obviously, I dont need that for the first set. But I do need a shorter preparation time so I can put my iPhone way in my jersey pocket after hitting start. Normally, I would rate an app as a 4 if it missed a key feature but this one still deserves a 5. It is so well thought out. For instance, you can use it on a big screen because it plays well with AirPlay and Apples external connectors. What other exercise apps do that? That means you can lead a class using just this app!