I haven't made any attempt at using the steering wheel controls. It just hasn't really been something that I wanted to do. Though, I have been meaning to implement some analog style volume control, just haven't gotten around to it.
I've been meaning to update the thread anyway, so I'll add this here. One thing that I have done very recently in the last couple of weeks is install a tplink TL-MR3020 mobile router. Got it for cheap at $30 and it allows me to run my LTE internet stick and automatically connect to the internet when the car is powered on. It gets its power from USB, so very simple to add on to the system. Normally with the internet sticks you have to manually run their software and manually log in each time. With the TPlink it is automatic, and separate from the OS. Now my car is a hotspot as well since the TPlink is a full wireless router. On top of that, I installed Plex which allows me to gracefully stream videos to any device that can wirelessly connect to the router, and has a great interface for the mobile device. I have encoded videos to h264 in such a way that most relatively current mobile devices (such as android) can play them directly (as opposed to the carputer having to spend CPU transcoding). So far I have tested having two simultaneous devices streaming videos from the carputer, and they work flawlessly with no resource impact on the carputer. They are at 854x480 and very good quality. To that end, my main goal is to install my touchstone inductive charger for the backseat so that I can put the hp touchpad back there as needed. That way it can provide video and audio entertainment completely independent of the head unit (other than streaming from it). Not a lot of options back there for mounting, so I'm trying to think of something creative which is probably the biggest hurdle in all of this.