I have noticed lately in the Sporty's cataloges that iPad and Smartphone apps & accessories for pilots seem to becoming more of a trend lately.

I still thought the electronic flight computer was a radical, revolutionary idea....

I was under the impression that the use of a phone was against the regulations while PIC, but now I can use it as a tool and a resource while flying?

Have FAA regulations changed or evolved to allow pilots to take advantage of more portable electronic gadgets, and are they officially approved for such uses?

It's worth noting that there are quite a lot of apps out there which are most used at the preflight stage, as opposed to in flight.