Have a vehicle without Bluetooth connectivity? The Jabra Drive Bluetooth speaker may be just the tool you need. I've used this device for over two years, and with few exceptions, find it easy to use, and extremely portable. I regularly use it in our two vehicles for both phone calls and GPS directions while listening to music and local information on the radio. Pairing the Jabra Drive to my iPhone is straight forward, though on occasion having exited and returned to the vehicle a few times, it will need to be restarted to automatically pair.
The audio is more than loud enough, as long as I make sure the audio levels on my phone are turned up, and with the exception of top-down driving on the Jeep, the microphone easily captures my voice for both calls and Siri.
If your vehicle does not include Bluetooth connectivity, I highly recommend the Jabra Drive.