Sometimes you get a bad moment when the recourse to prayer looks more natural than ever. You can send a message to all those who have installed the app and some of them will pray for you. There may be a thousand, might be a hundred, could be a single person who is praying for you. You do not know who prayed for you, but you know the number of those who did and even just knowing that somewhere in the world someone thought about you and prayed for you will likely help you strengthen faster.
And whether your prayer is a natural everyday act and you feel that through your prayers those who are in need can be helped, then pray for them. And if the prayer will not take visible effect immediately, they will know that you've thought about it and this will strengthen quickly and give them a little more hope.