Monster's iCarPlay tape adapter is total Apple Store iPhone retail bait. Why was it irresistible on checkout? Because fat-jack aside, my old one was highly susceptible to iPhone's self-inflicted GSM buzz: the dreaded EMI that speakers exhibit when placed near cellphones. Did this fix it? Despite the Compatible with iPhone sticker, NO NO NO NO NO NO!
The Good:The headphone jack fit perfectly with the iPhone's recessed headphone jack. (The old one broke after I lopped off the adapter's plug trying to shave it down.)
The Bad: A simple test revealed that the Monster was no more resistant to the GSM buzz than the 10-dollar version from RadioShack. This one is $25.
Verdict: If you're trying to kill the iPhone's self-inflicted GSM buzz, forget it. You're better off shaving the extra plastic off your old one. Careful, now, careful! And Monster, we'd like to think that if anyone can shield a tape adapter from GSM EMI, you could, so get working on it. And maybe change that Compatible with iPhone sticker to Kinda CompatibleZZZZZ withZZZZ iPhoneBZZZ!.
(I would switch to airplane mode, but you know what? I don't want to miss calls because I'm listening to music.)