This app was mentioned in 2 comments, with an average of 2.00 upvotes
Runtastic's timer allows you to set intervals and such. It is decent, but I haven't spend much time looking for alternatives either.
https://play.google.com/store/apps/details?id=com.runtastic.android.timer
Wouldn't a workout timer work for this? Something like https://play.google.com/store/apps/details?id=com.runtastic.android.timer but with vibration instead of sound.