With smartphones becoming more commonplace, you see these devices a jack of all trades. Why not use it for their car stereo? Although this is currently only a Kickstarter project, Dash — The Smartphone Car Stereo is an example of where mobile and auto audio is heading: everywhere.
The concept here is pretty simple: many cars nowadays come with what's known as a double-DIN sized car stereo, which means that it measures 4" x 7". The Dash base unit would mount into your dashboard using whatever mounting equipment is necessary for your particular vehicle, then you would purchase a separate plate specific to your phone model, providing a dock for you iPhone or iPod to charge, play, and be used as a replacement for both radio, DAP, and navigation unit. The Dash is rated at 4 x 50w to power speakers, with 2 preamps running at 2V a front and rear/sub.
As of this writing the project is still $30k away from funding, but with some support, this could be a very cool concept. Check it out!