What heights can electrical wiring be fished through wall studs?
Your situation isn't unique, and any wall is likely to have wiring in it at various heights. It should be centered horizontally, so if you limit your fastener depth to about 1-1/4" you should be safe. If that's not deep enough you're probably not using the right fasteners. Wires and pipes that are close to the stud face should already be protected with steel plates. 

Of course, you can purchase a non-contact voltage detector to trace the wiring, but this shouldn't be necessary.