Update: The RadTech team has responded to this post (see comments below) and asked me to evaluate a more recent revision of the WaveJamr that resolves many compatibility issues. As soon as it arrives, I'll give it a try.
No doubt, the idea of the US$39.95 WaveJamr audio adapter is a fine one. Got a healthy helping of 30-pin dock devices around the house or in the car? RadTech's slim, control-free WaveJamr pops neatly onto the dock connector, and allows any Bluetooth audio source (like your iPhone or iPad) to connect and transmit.
Requiring no power and almost no configuration, the WaveJamr seems at first glance like a wonderful solution for your older docks if you want to use them with Lightning-equipped current generation iOS devices. There's only one slight flaw in the plan.
Unlike iLounge's reviewer, I didn't notice any major audio distortion with the WaveJamr. What I noticed was a complete lack of audio. On dock after dock that I tried -- a Panasonic bookshelf unit, the Pure Contour 100i, the Time Command mini -- the WaveJamr would power up and pair with my phone, but the dock simply did not recognize that an iPod or iPod-equivalent was docked.
I was just about to throw in the towel and call it a defective unit, but I finally found one dock (the Edifier Luna5 Encore) that consistently did recognize the WaveJamr and allowed me to play music from across the room. Audio performance was perfectly acceptable, once I got it working.
RadTech sells a combo USB and 3.5mm headphone jack adapter to go with the WaveJamr, making it compatible with cars or stereos that don't have a 30-pin dock. At $24 for the cable, it might make sense for a room stereo, but in a car I'd say just plug into the headphone jack and save the money.
If you're on the hunt for a 30-pin Bluetooth adapter, there is a suite of units from Exeter and Bell, all of which appear to be built on the same base hardware as the WaveJamr. At about $32 street price, just make sure you check the return policy before you buy. If your luck is better than mine, you may enjoy some nice mobile sound. As a quality alternative, one of our commenters suggests the Kickstarter-funded Auris adapter, which runs $50 and pairs with up to eight devices. Unfortunately it's back-ordered until February.