At Sandia National Labs, they have ported Inferno to devices that currently run Android. Although it uses the underlying Linux kernel, it replaces the whole Android Java stack, which makes it very efficient, fast and completely free.
A device with Inferno would no longer run Android, it would simply run on the same modified kernel as Android.
Personally, your editor does not consider this a development for end users, but rather a demonstration for manufacturers or interested people of the versatility of Inferno and of the possibility of building another operating system for mobile devices with Inferno.
More info: https://bitbucket.org/floren/inferno/wiki/Home
Video: http://www.youtube.com/watch?v=dF_-jQc53jw