Are you still working on this Fabricio?
I'm not sure if it would work, but supposedly holding the Home button triggers "android.intent.action.ASSIST" to be broadcast. You could try to catch that and display and overlay in any given app/screen.
Interesting!!! Although i'm not on factory ROM anymore (using Cyanogen now, so i'm adapting launcher to it, adding more functionality), maybe it's still intercepted by Ouya framework... Will do some testing.
Anyway, how did you find this one? Never have seen this on any Ouya official documents, and never saw that on logcat, but hey, i never read all logcat, so i may have skipped it.
As some of you may know, I'm running a MOJO as my main box now with CM 12.1 at the moment. I hope it's OK, but I'm going to give this launcher a try on this box and see how that goes. I'm currently using the excellent Top TV Launcher but this is a little limited. Has anyone here tried the HEYA Launcher on a MOJO? Let me know.
Anyway, either way, I'll give it a go and post back if anyone is interested.