As far as features go, the Voyager 835 is pretty basic. You can answer and end calls by tapping on the multifunction button, and you can also check the battery power by holding down both the multifunction button and the volume down button for about 2 seconds. (The more the red LED flashes, the less battery it has.) The Voyager 835 supports last number redial and voice-activated dialing as long as your phone supports it. It also has the capability to transfer calls from the headset to the phone and vice versa. One great feature is that the Voyager 835 supports multipoint pairing, meaning it can connect to two Bluetooth devices at one time.
We tested the Plantronics Voyager 825 Bluetooth headset with the Apple iPhone 3G. Thanks to the Quickpair process, the headset goes automatically into pairing mode the first time it's turned on. Call quality was very good, because of the aforementioned AudioIQ technology and the dual microphone digital signal processing that eliminates background noise--one microphone captures surrounding noise while the other microphone focuses on your voice. Since the mics are omnidirectional, we didn't need to properly align the microphones to our mouths like with the Callpod Dragon V2, which is a good thing.
The addition of Windsmart technology is also very helpful in windy situations. We tested ours in front of a regular desktop fan, and were still able to communicate to our callers, albeit with raised voices. On their end, callers said our voice sounded loud and clear, but with a slightly tinny and hollow quality. That said, overall sound quality was still quite impressive.
The Plantronics Voyager 835 has a rated talk time of 5 hours and a standby time of seven days. It comes with an in-car charger plus an AC charger.