An iPhone is many things, but a massage therapist it is not.
However, if you're in a pinch, the lightweight application Massager may soothe you until your next appointment.
The application takes advantage of the iPhone's vibrating motor to create four patterns based on Swedish, Shiatsu, deep muscle, and relaxation massage. Starting and stopping the massage are easy enough to accomplish by tapping and untapping the corresponding button.
While you can manually increase the intensity of the vibes by putting some muscle behind the iPhone's flat face, it still won't come close to what a pronged handheld massager can do. After a few minutes, my wound-up shoulders remained just as tight.
Yet it might relax tension in you and yours, and at 99 cents, that's not a bad gamble.