iPhone compatible stereo Bluetooth

Just wondering if anyone knows of any particular brand/model of stereo Bluetooth that works properly with iPhone, particularly the 5.

I have a Sony Ericsson model, about 4 years old, which worked just fine with my Nokia N97, but with the iPhone it disconnects every time I make/receive a call, or try to use Siri. I know the Bluetooth on iPhones is poor, but surely there must be something that works right?