That's tough because most people would want stereo from thier iPod, so that's why you'll find most BT transmitters using the A2DP stereo protocol. (though I can imagine many uses for the mono headset too).
I don't think you'll find much inthe way of iPod (or regular audio jack) to BT adapters and transmitters that will use the mono protocol.
I'm looking to add some audio BT transmitters tomy website now and I haven't run across what you're looking for yet. If I do, I'll post something.
Jeremy
WickedGoodTech.com