Calling all Portal fans...
Valve's insanely popular Portal title has been unofficially ported to Android. Well, at least one level of the game has been ported to Android. Sadly, it's not Valve behind this project, so we can't say for sure if you'll ever be able to play a full version of the game on your Android phone or tablet. What we can tell you that the developers responsible for this port used the Unity engine to do it.
Android Police reports that "there's actually not much to play" and it's more proof of concept than anything else, but perhaps if we all cross our fingers and wish really hard, Valve will give us something we can actually work with. For now, this demo from a team of Russian developers is all we have. Savor all two minutes and nine seconds of it below. Oh, and in case you were wondering, Android Police says the choppiness you see is from their recording, and not the game itself:

HL3 anyone?
Steam games already have OpenGL support. That is how they run on MAC.
(even quake1 could get very close to this, ports even closer
A nice proof of concept anyway, but this is still lacks the essential elements which is a fully working placeable portal with render trough, the hardest part sadly
I guess one could do some clever texture that is actually an camera pointing from the exit (Kinda like how duke3D cameras worked), updating at a certain rate.
Good thing that portal1 was rather simple so not THAT much gamecode is needed to get much of the same feel.
unreal engine lisesnce at least the last time i bothered to look it up was 750,000$, not sure if other versions of the engine exist, and pretty sure that useing the engine for this is a no no...
that said if i had the skill to make an engine, why would i want to use unreal?