alarm app with vibration pulses rather than time set ?

Hi, looking for an alarm app that would allow me to custom set a number of vibrations rather than the stock app that only allows for time-based vibrations (like 30 secs or a minute), which is too long for me. Haven't been able to find one, but sure one must exist !

 

thx for the feedback. Not exactly what i was looking for. Maybe i expressed myself confusingly. Basically, i would like the alarm to vibrate let's say for 4 pulses, or for that matter, 4 seconds, so not so long as the minimum 30 sec vibrations in the stock app...