I think this app whilst well intentioned will do damage to people who are vulnerable in myriad ways. It will enable people to harass and bully other's more efficiently, it will cause people to feel guilty and responsible when they can't help their friends, it will cause discord and confusion between friends and acquaintances and it will mean that people will feel unsafe using social media and their voices will no longer be heard. As someone with mental health issues who loves people with mental health issues and wants people to be supported and that love and empathy and care are important I have signed this petition asking twitter and the Samaritans to pay attention to the large amount of feedback on this. (Feedback being given by people who use twitter and who have mental health issues, the very people this app is supposed to be for.) For some people this may be a life and death issue, vulnerable people who are already suicidal and then are exposed to abuse, and I don't want any of those lives lost.
(The reason I stress the love and empathy bit is not to say I'm a good person, trust me I'm under no illusions of that, or to say I'm unusual in thinking these things are important, it is to emphasise that the exact things the app thinks it is helping to spread are the things the system in practice lacks.)