I was watching my Google alerts today and an interesting presentation by Benjamin Zores he gave at Droidcon 2013 in Paris this week came up. I would have loved to have seen the actual presentation, but the slides give a pretty good summary of what he talked about.
The Growth of Android in Embedded Systems
He certainly raised some valid points in his conclusions, that (as I read it) Android isn't for everyone. Ice Cream Sandwich pushes the resource limits pretty high, generally due to graphics requirements. Benjamin's final conclusion states that Android is good for devices featuring an LCD screen and are primarily app-driven.
For non-UI focused devices, Android is only beneficial if you can turn off all that UI stuff and still maintain the power of the platform. It remains to be seen whether Google will see the vision in a Headless Android port (doubtful) so in the mean time, the heavy lifting is left up to individual companies.