Aren't burner phones that way because you want to ditch the entire phone to erase any link to you after using it in an incriminating way?

Even if this app was "secure", it wouldn't prevent the need to ditch a phone. LE can subpoena the company, find out which IP:port connected for whatever user/message. Then go to cell company and get records and track the cell.

Get an android and use textsecure if you actually care about people not reading your messages.

If you're using a burner I doubt the environment is your topmost concern.

Why would you even consider using this app?