The app was described as a "social network". As someone who has experience with suicide (both from my perspective and from losing people), I have to question what a difference that will make. How exactly does it work? If he can't explain, perhaps a mockup of the UI might answer a lot of questions.
Of course it has the potential to help someone. Everything has potential but how realistic is that? The chance that this will make a difference seems really low to me.
I hate to be the negative guy on HN but suicide is a serious matter and I can't see why anybody would give grants to 15 year olds to build 'apps' to 'prevent it'.