A nifty little app to agree on exchange rate +-%. I believe some apps already do that.
These gangsters charge fortunes to send small amounts of money around to developing countries.
The thing is, if I have trusted offices at both sides, I don't need Bitcoin, I can keep my own accounts. I don't know why Western Union charges so much, probably both regulatory overhead and transfer risks.
What Bitcoin provides is a trusted ledger, so independent parties can operate such offices around the world and use whatever exchange method they see fit. Sender would receive a private key as proof of transaction. Though there still needs to be a secondary communication channel between exchanges so that the sending party knows how much to send to match the correct amount on the other side.