I was pretty surprised that the Treo 600 microphone is pretty sensitive, so sensitive that I don't think I'll even bother investing in the Seldio 2 in 1 adapter. I found that if I leave it in my shirt pocket when I'm driving and listen via one side of my earbud headphones, they can hear me and I can hear them perfectly. Even on the train, I just leave the phone at regular PDA holding distances (foot to foot and a half?), and talk in a soft voice as to not disturb others on the train (pet peeve, people blaring into their phones like they're bragging about conversations none of us want to hear, they might not even be actually talking to anyone haha), and they can still hear me perfectly.

I bought a pair of Sony 74SL street style headphones, it does detach at 0.5m to attach to a remote (or the Seldio) but I really guess I won't be needing that feature anymore. Still a great set of headphones tho! And it matches my Treo!