This video shows off Portal being run on Unity on an iPhone 3G.

No one is clear on what this video, or project, will eventually turn out to be. We're not even sure if Valve is planning on porting the game over to the iPhone platform. Valve does seems to have a unexpected responses to spinoff projects, which this may actually be. 

TouchArcade quotes Portal Prelude, a fan-made Portal prequel blog:

Yesterday, we got our first contact with the french community manager of Valve. Yes, Valve. The marvellous company that brought Portal and so much more to us for years. Don't take me wrong, I'm not trying to seduce anyone, but believe me, it was huge. I was so happy and so scared at the same time. For your information, they don't seem to bother about us doing a prequel for Portal. They're even sending us their congratulations and they seem to enjoy what we're doing.

So, all we need now is a response from Valve about this project. In any case, we hope it's true and can be on the iPhone - then our productivity can drop to zero forever!