Seems like a very nice combo.
For me, I prefer using the iPhone/Harry's app as an instrument to tell my lap times, therefore I mount it on the windshield and use something else to capture the video. Then I download the data from the app, and use a software called RaceRender to overlay the data onto the video. Works great for what I need. Below is a video from an event last month.
Oh...for the cable, if you have the USB slot in the glove compartment, you can use it to have constant power for the phone. You can kind of see the cable in my video below.