Generally speaking, you're trying to keep the jackhammers, trains, horns, and loudmouths that pollute the world's airspace out of your head while you're holding that conference call and walking back to the office from lunch at the same time -- but Sound ID's new 400 model takes a different approach. The upcoming Bluetooth headset has a couple unique features that set it apart from the crowd, the first being its so-called "Environmental Mode" -- shared with other Sound ID models -- which allows for two-ear hearing between phone calls without going to the trouble of taking the set out of your ear (the people around you might fancy you a dork, but they just don't get it, and they never will). The other biggie is compatibility with the company's not-yet-released Companion Link remote mic, which allows a second person to join into the conversation or simply repeats audio back to the 400. Look for the set to hit shelves in the fourth quarter for $129.99, with the Companion Link tagging along for $79.99. [Warning: PDF link]