Defective by design
In the first version this didnt ring if the screen went blank before time was up (a simple bug, and one that was reported as such). Now the author has decided that it is easier to disable the screen blanking entirely rather than make the app work properly. Using this, your iPhone will be lit the whole time, running down your batteries and disturbing the darkness of the room (and possibly damaging your screen as well -- it cant be healthy to have a static image displayed for a solid 30 minutes or more).
The author clearly chose to take the lazy way out and hide the defect in this program rather than address the user complaints and fix the bug in an honest manner. As such, I can not in good faith recommend this program to anyone.
Lograh. about
Meditation Timer