Simple communicator for stroke victims

This was the post I started to write:

I just started learning Arduino; been working through the examples and making my own breadboard toys with a photoresistor, a servo, and some LEDs. At the same time, my grandmother just had a severe stroke. She is near-vegetative, but has some control over her eyes and a foot and seems to recognize and understand us. We're not sure she can feel her foot when she moves it, though, so we want to provide her some more definite feedback to help with communication and recovery.

I ordered a LilyPad Arduino and 3-axis accel from SparkFun, plus a bunch of components that I'd like to sew into a sock, but in the meantime I'm trying to hack something together with what I have on hand, which is a few photoresistors, LEDs, servos, and a small collection of components like resistors and capacitors, and a speaker. So what I'm trying to do is build a light-triggered "mouse button" that she would activate by blocking the photoresistors with her foot. When they're shaded, it will blink some LEDs and play a tone, and when they're exposed again the LEDs will go off and it will play a different (momentary) tone, so she'll have clear audio and visual feedback.

While I was putting it all together this afternoon, I got word that she had died. I'm still going ahead with the project, though, because it could be a useful thing anyway, and it's still a good challenge. I solved the original problems I was going to ask about, too, so everything works now. But as a next step, I would like to have the speaker play words, like "YES" and "NO". Can I do audio like that on a simple Arduino setup? How?

I believe the phrase you seek is "pulse code modulation" or "PCM"... yup...

Sorry to hear about your grandmother. I hope your project is a success.