http://www.wired.com/gadgetlab/2009/12/iphone-university-abilene/

Good article.  It's funny because I do this all the time.  When a professor mentions a topic I don't know about, I will immediately Google it on my iPhone.  Sometimes the professor will ask "Anybody know..." and I will Google that and answer the question.  I think it helps me to be more engaged and active in the classroom. 

There are a lot of arguments for not having laptops in classrooms (because seriously the iPhone is almost a mini laptop) but I think that those people who play Solitare and check facebook during class on a laptop, would just be the ones texting friends or sleeping, whether or not they have a laptop.  

In the end, I think that supplying students with tools they can use to be more actively engaged and invested in the lectures can only help.