I've tried a few OBD-II dongles and by far the best I've found is the GoPoint BT-1 Bluetooth. It's expensive at $120.00 (U.S.) but it links flawlessly with HLT on an iPhone. Since it's Bluetooth, you can simultaneously use the iPhone's wifi connection to link a multicam Go Pro camera for PIP.

External Cam Only Mode is my top priority. My iPhone 6s Plus video shakes so badly I need to use something else.

Hi Harry, I too have shaky, blurry video. I'm using an iPhone 6s at Sebring, which is a bumpy track. My phone is a new 6s Plus. I had the same results there with my prior iPhone 6 Plus. I have tried several types of windshield mount, each of which seems quite solid and stable, but still get the same...