As far as I can tell, there doesn't seem to be any way to send data back and forth through SMS messages without the built-in Messaging app also receiving all the incoming messages. If that's the case, then how does the Instant Messenger app send messages through the SMS system without all your incoming IM messages being dumped into your Messaging app as well? It seems like there must be a way to use the SMS system the same way that T-Mobile's IM app does.
I was also wondering about the reverse case, is it possible to send an outgoing SMS message and have that message show up in the default Messaging app?
Basically, I'm trying to write a program that receives a command string in an incoming SMS message, then sends a response SMS back with some information in it. I would either like none of those messages to show up in the messaging app, or I would like both the incoming and outgoing messages to show up. So far, all I can get is for the incoming messages to show up but there is no sign that a response was sent, which is sort of confusing to the person on that end and they don't know if they need to write an answer or if it's already handled.