Amal, please bear in mind my primarily concern at this point is marketability. Having to string additional wires inside a car is, I believe, a liability to widespread acceptance - and, trust me, you really don't want to exhaust the valuable time, thought, resources, etc demanded by a false start if you can help it. They are painful, disheartening and expensive. A motivated volunteer sales force requires the diametric opposite.
People today are irritated enough having to deal with a tangled USB cord in their cars (if they don't have a mobile bluetooth or wireless connection). And those who drive a high-end/status vehicle are not going to look kindly on the appearance of a cable/reader/antenna if they consider it unsightly. Thus the issues: convenience & appearance.
Now, regarding your line above, "more power than a battery can supply long term," these days nothing is long term - and folks have actually grown accustomed to it. Just ask my 96 year father-in-law how long his hearing aid battery lasts ; - ]
But having to change out something the size of a 9v battery every month? That won't be a dealbreaker. It can be done the same time they replace the batteries in their wireless LED strings for the pantry, etc, or their smoke alarms, remote controls, 3D glasses, fitbit, etc. Furthermore, if YOUR battery were rechargeable, the cig lighter socket could then be used to keep a replacement battery charged (and, for better or worse, would also add value as a 'conversation piece').
Again, the goal is to facilitate maximum public acceptance (or better: minimize rejection) of a truly wonderful, cutting edge concept, which, like every novel idea throughout history, is sure to cut down at the outset by many, and for all the wrong reasons.
P.S. Yesterday I spoke with the aforementioned AV guy, an expert at creating promo videos - and he is excited about being involved. Not at all surprising. If you and your disciples can revisit and resolve the 'convenience and appearance' issues, the little folks like us can do the rest.
P.S.S. One of my first promotional objectives would include linking your product with a major sponsor - like Honda. Major sponsors are always the first to ask, "what's in it for me?" The an$wer is obvious! Of course all such courses of action will need to be pre-approved by you.
All of this...for your consideration.