There are a bunch of interval training apps on the app store. This is a good free one I use myself: https://itunes.apple.com/us/app/interval-timer-seconds-by/

There are a bunch of interval training apps on the app store. This is a good free one I use myself: https://itunes.apple.com/us/app/interval-timer-seconds-by/id475816966?mt=8 https://itunes.apple.com/us/app/interval-timer-seconds-by/id...