If you can see what data is leaving your phone, and you don't trust the author, then I don't see what difference the server side code being OS makes...? There'

If you can see what data is leaving your phone, and you don't trust the author, then I don't see what difference the server side code being OS makes...? There's not really anything they can do to comprehensively prove what they do with the data after it has been received. What are your concerns with the data it sends?