Hi,
You may be interested in Processing, http://www.processing.org - it's a very similar language to the Arduino/Wiring language. I've seen something you may be interested in, http://accrochages.drone.ws/en/node/90 - an 'oscilloscope' made using an arduino's analogread and sent to the computer over serial for display in processing.
I'm sure you could add some code to wait for a larger duration between readings, and/or adjust the code in processing to average lots of readings before generating a new value on the graph.
Have fun!!
Ed
