Works great for me.

I shoot .45 cal for IDPA. This app is great. Have no problems. The phone is on table no more than 4 away. Being fair, I am by myself on range. The tone is loud enough to hear with ear plugs alone. Its free you have nothing to loose. Great app for someone who doesnt want to spend $120 on a timer.

Joe hawkins1488 about Gun Shot Timer, v2.2