For the last two years, I have used an iPhone car mount in my car (first the Kensington LiquidAUX and then the Kensington AssistOne). I can't imagine driving without using a device like this. Because my car lacks built-in Bluetooth, the $99 AssistOne is a great option for me. If you just want a window mount, you can buy something simple such as the $19.99 Griffin Window Mount. Earlier this year, Griffin released an enhanced version of that device called the AirCurve Window Mount, and they sent me a free review unit of this $39.99 device which combines a car mount with an acoustic amplifier.
The AirCurve Window Mount comes with four parts. You get a mount that holds an iPhone 4 or 4S. You get an arm that attaches to the mount. Then you get to ways to attach the device to your car: a mounting base that sticks to your dash, and a clear plastic base that clings to a window using static electricity.
I didn't try the mounting base because I didn't want to attach anything sticky to my dashboard, but I did try the removable clear plastic base on my windshield and it seemed to work well. Just clean your window and then press down the base and remove all bubbles. This creates a connection that seemed quite sturdy to me. (I did see, however, that one reviewer on Amazon complained that he had trouble getting the base to stay on his window.) Then you simply slide the arm into the base and attach the mount.
There is enough space in the bottom of the unit that you can attach an iPhone connector. Thus, if you have an iPhone charger that connects to your car's power outlet, you can charge the iPhone while it is in the mount.
What makes the AirCurve Window Mount different from other devices that hold an iPhone in a car is the AirCurve has a small hole near the speaker on the button of the iPhone which leads to a larger hollow area behind where the mount holds your iPhone and then to the large opening along the right side of the mount. This space works sort of like a horn and is an acoustic amplifier.
Thus, if you are listening to something on your iPhone without using an external speaker (such as Bluetooth to connect to your car's stereo system), it will sound louder when your iPhone is in the AirCurve Window Mount. Griffin says it will be up to 25 decibels louder. To my ear, it sounded almost twice as loud. The iPhone in the AirCurve Window Mount with the volume turned just slightly more than halfway sounded just as loud as the iPhone outside of the unit sounded with the volume at its maximum. And if you turn the volume all the way up when the iPhone is in the AirCurve Window Mount, the sound is almost too loud, especially if you are listening the music where the sound becomes distorted. Thus, when you use this device, podcasts, spoken words or a phone call sound louder and better, and music sounds louder although still not nearly as good as when you are using your car's stereo.
When my iPhone phone was in handsfree speaker mode, the sound of my voice didn't seem any different when I was speaking with the iPhone out of this device versus when I spoke and the iPhone was in this device. In other words, when used with the phone, the other person will sound louder to you, but you shouldn't sound any different to the other person.
My only complaint with this device is the adjustable arm is not very long. I'm used to the very long arm on the Kensington AssistOne, which places the iPhone just over the dash in my car and makes it easy to connect cables. Here are the two units side by side so you can see the difference, just in case this is significant to you:
If you want a way to mount your iPhone in your car but you don't want to connect to your car's stereo, the Griffin AirCurve Window Mount is a clever solution that gives you the option of making your iPhone even louder. As Nigel Tufnel might say, this device lets you turn your iPhone up to eleven.