I want to control and Ardunio by writing bytes to it in the same way I would use the serial monitor on my laptop. How could one accomplish this?
You can by using pySerial.
This will allow a console based python script (or a python GUI program even) to listen/talk to you Arduino.
That's the route I took to make my generic Arduino DIY CNC machine. If your interested you can check it out at: http://emc2arduino.wordpress.com/