disclaimer: work at Amazon, nowhere near echo
The thing I really really want from them is echo in the car.
The right choice is probably a replacement nav and head unit. I'd rather have an old but nice car with great nav/ ent/etc, than a new car. I don't think I'm that unusual. I'd like to upgrade the electronics every couple years; happy to keep a car for 10-20y. Somehow those should mesh, but don't.
http://www.geekwire.com/2016/ford-working-on-amazon-echo-int...
At that point it's basically worth building a car computer. Possibly using Alexa for the voice, but if I'm doing a car computer, I think a hack to work with Cortana or Google or Siri might be easier.
It's amazing no one has done a good job of this yet -- it's been within feasible for 10y, and commercially viable for 5y for big companies, or 2-3y for startups just using existing hw. I think it's because not enough good product/dev/etc. people have 1h+ car commutes.