Look, another ‘bizarre phone app’… *shakes head*
Don’t capitalize app; it’s not even a full word, much less a proper noun.
The first sentence is compound. Add a comma after die. Add a comma after accurate, too, while you’re at it.
Spell out one hundred percent.
Capitalize There; it’s the first word of the second sentence.
Replace the em-dash after though with a colon. (This is the “more information follows” use for colons.)
I changed the placement of only to make the sentence more clear.
When referring to a word as a word, italicize it instead of using double quotes.
There’s a hot new app that can tell anyone how they will die, and it is always one hundred percent accurate, even if they try to avoid it. There’s one problem, though: the results for anyone born after the creation of the app come up only as suicide.