Powered up and hanging from its perch on your vehicle's visor, the BlueAnt S4 is always listening to you. If that seems a bit too "Big Brother," fret not. The S4 is only listening for a specific voice prompt. Simply say, "BlueAnt, speak to me" and the Bluetooth speakerphone springs to life ready to do your bidding.
Physically, the BlueAnt S4 doesn't deviate too much from the formula we've come to expect from visor-mounted Bluetooth speakerphones. It measures 4.88 inches long by 2.38 inches wide by 0.62 inch deep; the device's face is split between a gloss-black panel and a mesh grill that covers the loudspeaker, separated by a brushed-metal band that bears the BlueAnt logo. Just beneath the gloss black front edge are three hidden color LED lights: blue for connection to Bluetooth, green for listening mode, and red for battery state.
Where many devices use snap- or slide-on visor clips, the S4 has a pair of strong magnets that connect to the device's pair of interchangeable visor clips: one for narrow sun-visors and another designed to grab slightly thicker visors.
Along the S4's left side is the three-position power switch and, beneath a rubber flap, a Micro-USB port for charging and firmware updates. The power switch is the S4's only physical control. The rest of the user interactions are either voice controlled or accessed by swiping or tapping the device's touch-sensitive front edge. For example, swiping from left to right increases the volume, and right to left decreases. Tapping the device brings up the voice command prompt, or answers or rejects a call.
Along with the S4 speakerphone and its visor clips, users will find a 12-volt USB car charger, a 12-inch Micro-USB cable, and an extremely thorough user guide--a rarity with gadgets these days.
The BlueAnt's most interesting feature is its hands-free trigger mode. While in trigger mode, a green LED is illuminated to indicate that the BlueAnt is listening for its activation phrase, "BlueAnt, speak to me." When the device hears this phrase spoken, it goes into listen mode and becomes responsive to its full list of voice commands. Users can ask the BlueAnt for information about its pairing state, update the phone book from a paired handset, check battery status, or query the S4 for a list of available commands.
Of course, users can also make hands-free phone calls. Incoming calls can be answered or rejected by saying "answer" or "reject." If, during pairing, you allowed the BlueAnt to upload your phone's address book, incoming callers will be announced by name.
Interestingly, the BlueAnt S4 doesn't seem to have its own internal voice dialing system, instead deferring calling duties to your paired phone's voice dialing system, if available. Outgoing calls are initiated by saying, "BlueAnt, speak to me" then "Phone commands" to access your paired phone's voice command system. If your phone doesn't allow access to external voice commands, as is the case with Android phones, then you're out of luck and will need to initiate your calls from your handset. This is more of a limitation of the paired phone than that of the BlueAnt S4 itself, but other systems like Ford Sync or Kia's OEM hands-free system get around this hurdle by running their own voice dialing software.
In addition to hands-free calling, the BlueAnt S4 also supports A2DP audio streaming for listening to music or receiving turn-by-turn directions from a running GPS application. The unit also supports multipoint pairing for connecting to two devices simultaneously. When connected to two phones, the S4 can receive calls from either handset, but can only stream A2DP audio from the primary phone.