Or even just conduit between all the common places we would need to run cables.

or just pre-installed dashboard speakers with an AUX input and single volume+power knob. very cheap off the shelf parts. would save customers from weird bluetooth speaker setups, and would support a wide variety of devices – from iPods to tablets to pocket radios.

no speakers and low range are the only two things I'd quibble about. and maybe the price, seems too high for what you're getting.