Well, that was fast. Just yesterday, we took a look at Mozilla's Boot2Gecko booth at Mobile World Congress, where they used a Samsung Galaxy S II with modified software as the hardware platform to demonstrate their new OS. Already, a developer over at XDA-Developers has a version of the OS already packaged up and ready to be installed on the Galaxy S II, at your own risk of course.
Sensibly, the build is still in the pre-alpha stages and is not recommended at all for use if you actually need a phone. However, if you do just want to try things out, both cameras, video, audio, Wifi, and web browsing should work in the current build, and other things may work sporadically as well. A .tar package is provided for installation, meaning that you will have to use Samsung's ODIN update program to install the OS, which includes a custom kernel as well as system files and data.
It's worth repeating that this is by no means something novice users should try, and is not an official build from Mozilla either. What we have right now is simply a community developer taking advantage of Boot2Gecko's open nature to make a pre-alpha build for the Galaxy S II. Still, this is quite an impressive proof of concept, and I'm eagerly awaiting an opportunity to try Boot2Gecko myself.[XDA-Developers]