Do they actually teach that electricity is of the devil? I'm not sure that's exactly correct.
I went on an Amish
tour this past summer. It was explained to me (by the guide), that some of the men are allowed to have cell phones, if they're needed for their work. But they can't bring them into their house. The tour guide said that technology is only viewed by the Amish to be evil to the degree or extent in which it separates their families. And that's what they view as being evil: the way technology pulls families apart. I think there's a lot of wisdom to that.
In addition, we saw many Amish eating and working in the restaurants throughout Lancaster.
Each group or "church" has different sets of rules. Each group had a slightly different dress code and different colored buggies... Within Lancaster county, there are several--I forget exactly how many. Some allow the kids to go off on bicycles and roller skates, while others don't. Some use the really archaic farm equipment such as horse drawn plows while others are allowed to use tractors.