Uh... as I read it the point of this app is the the whole world is able to read your messages. This app is just the existence proof that all that is required is access to the raw packet data.
Clearly most people are going to "trust" Apple Computer more than this app vendor. But the point is that such trust isn't worth anything. The data is hanging out there already.
Huh? So, does the existence of an open-source reimplementation of early versions of SSL also imply that if you had access to the raw packets you can read anyone else's SSL stream? How about if we first require the data to be sent in the clear to someone who refuses to tell us how DES works, but is willing to provide a web service that implements it? This app is not by any stretch of imagination proof that the protocol on the wire is not encrypted. Yes, that might be the case, and we might learn some interesting things at pod2g's talk on iMessage at HITB (I'm definitely looking forward to that), but that would be totally unrelated to the existence or possibility of this app.
Clearly most people are going to "trust" Apple Computer more than this app vendor. But the point is that such trust isn't worth anything. The data is hanging out there already.