When plugged into your iPod the Gear4 AirZone FM Dock works just like any iPod dock, although incidentally it isn't certified as iPhone compatible so if you do wish, as I did, to use it with an iPhone you'll get an annoying pop-up informing you of that fact every time you plug it in. On the plus side, receiving a phone call didn't actually cause any interference, although using a car radio as a hands free set isn't, to my mind at least, isn't the best solution.
The AirZone draws all its power from the player it's plugged into, and if the numbers on the back of the device and my maths are correct, it draws a mere 300mW of power. The range and volume of the AirZone are fairly mediocre. Subjectively, I usually have my radio set to about 35 for radio listening but to listen to the music streaming from the AirZone required pushing that up to 50 - subjectively that would be ear-bleedingly loud in other circumstances.
The problem with this is two-fold: first, if you decide you want to change to a radio station you'll probably find yourself suddenly loosing your grip on your steering wheel in order to shield your aural cavities due to the sudden increase in volume. Second, when the signal from the Gear4 AirZone drops off, which it does occasionally, you'll also get a healthy dose of high-volume static.
Normally with an audio product it would seem pertinent at some point to talk about sound quality, but it isn't really applicable here. The music (or any other MP3 content for that matter) played via the AirZone sounds as good as anyone has any right to expect from what is essentially an FM source.
Comparing to the competition, the Gear4 AirZone FM Dock definitely doesn't do anything wrong while conversely doing everything it claims to be able to. On that basis then, it's hard to criticise, so I won't; the fact that all you have to do is plug the AirZone into your iPod's dock connector saving the hassle of a trail of wires polluting your car's cabin is compelling enough. Plus, with a suggested retail price of £19.99, you're not breaking the bank to buy one by any stretch of the imagination.
I asked before whether or not the Gear4 AirZone FM Dock could replace the Moosik CK3000-HD as our iPod FM transmitter of choice. The answer is yes. The AirZone is both a cheaper, simpler and more elegant solution than its competitors and thus if you're in the market for such a device, we'd recommend the Gear4 AirZone.