The last "Danger" smartphone -- some say still the very best smartphone for its time -- used NetBSD under the hood. It was really fast and responsive, small, easy to fit onto the processor -- all from a buddy of mine who worked at Danger in SW. Danger did the App SW, which was also very good. But it was NetBSD under the hood. My buddy showed an early prototype to me at the time, and I was jealous.
I do not know if the mods needed to run NetBSD that platform ever made it back into MAIN. ('cause BSD license and all)