We have Mennonites and Amish of several orders around here. Some of the Amish have headlights, brake lights, turn signals, and strobe lights on their buggies plus diagonally striped reflective tape. The ones that live nearest me can't even use a SMV symbol, just the black reflective tape, and have staggered height kerosene lanterns on the buggy so you can see them coming at night. Those of you who have Amish neighbors -- ask them about the Swartzentruber Amish and see what they think of them. Around here the other Amish treat them like second class citizens.
The more progressive groups can set up a business which is allowed to own things like phones and computers, but they can't own them personally. They can use certain machines in their business or farming, but not others. It all depends on what their bishops rule at any given time and whether or not the individual person cheats on the rules. The guy who runs the sawmill nearest me can have a 200 hp Cummins diesel running the circular saw to make lumber, but isn't allowed to use a chainsaw to shorten the logs because it isn't stationary. The guy who runs the bulk food store can have electric coolers outside the store and computers in the store, but their phone has to be a community phone in a separate building and the lighting in the store has to be from gaslights. The electricity is from their generator, not the grid.