The sacral anterior root stimulator is described as an implanted receiver and external transmitter system with different settings for bladder, bowel, and erection control.
I was offered the option of having the implant when I was in hospital. There is a receiver placed somewhere in your lower stomach and connected to a few strands of your spinal chord, and a transmitter to trigger the required reaction.
The transmitter has three optional dial settings and, when placed on your stomach and activated, stimulates the relevant organ to respond.