Wierd iPhone screen?

[slsl0]

I just got the iPhone 4 wasn't really paying attention to it and it popped up with a screeen that said

"Pwr on/off" and an accept or cancel button, I didn't take a pic and i just pressed cancel, anyone know what it is?

 

[saving107]

I remember getting that same screen in the first week of getting my iPhone 3G and in the first week of getting my iPhone 3GS.

I remember I googled it and found a blog that explained it, I'll try and look for it again.

 

[Sirobin]

I got that. I assumed it had something to do with activation...your guess is as good as mine though.