While restraining orders are meant to keep people away from each other, they can't tell when someone has breached the border of how close they're supposed to come. Because of that, sometimes it's too late before someone finds out that a stalker or a jilted ex is on their way. Because of that GPS might start coming into play in restraining orders.
For people who seem especially dangerous, unstable, or violent, they may get a GPS tracker attached to them. If they come within a certain distance of the person who took out the order, they'd be notified via their cellphone. If the person left the area, they'd be notified again. It would be a near foolproof way to make sure people follow their restraining orders, one that has the potential to save lives.