This is so simple and cheap and it just might work.
http://www.thinkgeek.com/electronics/audio/6bd8/
Have you ever seen those? They supposedly turn any surface into a speaker. I heard that they're not very good, but I'd love to get one to stick on my guitar. I remember reading about a DIY project about sticking a small speaker on the back of your pickups. Anyways, just an idea. Since I live in an apartment, I'm hoping this may simulate the interaction between guitar strings and sound waves from a cranked amplifier.
http://www.diystompboxes.com/smfforum/index.php?topic=8642.msg52120#msg52120
http://www.soundbug.biz/