The Echo Auto doesn't have an FM transmitter, so if you have an older car without an aux port or Bluetooth, you still need an FM transmitter to use it. Incorporating an FM transmitter would be a differentiator. So would a heads-up display.
I'm conflicted now about whether to use the Echo Auto with the FM transmitter I already have or whether to go with the Roav Viva Pro if I can catch a sale. Suppose it makes more sense for me to try the Echo Auto as I already have the transmitter.