I purchased this one, and received it a few days ago:
Very small and compact, and what's great about it is, it has a mic and answer button.
If a call comes in while you're listening to music, no need to stop the music, or unplug your headset... the music will stop automatically, you simply press the answer button on the adaptor, and you'll be able to answer your call.
The sound, from my Vibe headset, while answering a call, sounds a little echoy, but nobody has complained on the other end about how my voice sounds to them. I can hear them fine, it's just I'm listening to a phone conversation through music headphones, and again, there is a kind of "big stage" sound, if that makes sense.
Once you're done with the call, press the button again, your call hangs up and the music continues from where it left off!
Nice!
Just make sure you plug your headphones into the adaptor 1st, THEN plug the adaptor into your G1. Not sure why this is, but this is a common issue with Seidio (the manufacturer) adaptors.
You can find it at
www.seidioonline.com
$15 plus shipping.