Id's put its mobile projects on hold while it finishes up Doom 4, but that hasn't stopped one enterprising team of developers porting over the previous instalment, Doom 3, to Android. Your entry to Hell just went mobile.
In the video, rather tediously, the game takes forever to load, so skip to around the 1:55 mark to see the engine actually work. The port is currently in a pre-alpha state, but even on the relatively old HTC Desire HD, the devs are apparently getting in the region of 26-30fps -- that's definitely playable.
Hopefully it'll load a tad quicker than that once the port's finished, especially on the likes of the Nexus 7. When it'll finally be playable and released for your gaming pleasure, I'm not sure. But you can get in contact with the developers to help out if you're keen. [Google+ via Phandroid]