No, one sensor with two wire loops molded in at different positions. The sensors only start to wear when the pads are getting close to worn out. First loop cut and you get a service due soon warning (or something along those lines). Second loop cut and you get a service due immediately warning (or something along those lines). There is no sensor that actually measure the pad wear continuously. So, the mileage to service indicator is an assumption based on average pad life as determined by BMW. I have no idea if the computer takes driving style into account and adjust the mileage estimate accordingly.

Edit: You should also know that there are two loops in the sensor, but still only a two wire sensor. When one loops gets cut (worn through), it changes the resistance of the sensor as measured by the computer. When the second loop gets cut, the circuit is then "open".