Girls, I read a book once where the main character had some kind of…

Girls, I read a book once where the main character had some kind of contraceptive implant under her skin. What is it? An implant? It's expensive to get and who has gotten one? Does it help? I don't want to take pills, they make me nauseous, and the coil isn't reliable. How many of my acquaintances got pregnant with a coil. Condoms aren't always effective.