I just learned that Firmata can be combined with servos.
In the Arduino IDE is an example: File / Examples / Firmata / ServoFirmata
For your own protocol, go to the Serial page
On the right are some examples, click on ReadASCIIString
That show how to use it, with Serial.parseInt.
This is a tutorial with Serial and Servo
http://playground.arduino.cc/Learning/SingleServoExample