Short Alarms is a simple application that makes a sound and vibrates at a configurable time interval.
It also can be configured to alert forever or a limited number of times.
The sound that's played in the app is no longer than 5 seconds. It's an unattended alarm in the way that you don't need to press anything to stop the sound. It's just an audible notification.
If the repeats are setted to 0, the alarm will sound at each interval forever until you hit the cancel button.