Ambience: As you probably found out by now, GSRs are about $150 US without accessories. They take the Galvanic resistance of the skin and produce a beep or tone. A high pitched tone means your tense and a lower tone means your relaxing. I'm sure there are lots of web retailers selling GSRs.
EEG devices are good but if your goal is to meditate like a guru I'm not so sure they'll help you since you'd be getting only visual feedback and you'll be meditating with your eyes closed! Usualy only Bioffedback Practioners will dish out that kind of cash for a machine.
There are lots of ways to get into meditation, Biofeedback is one of them and it's probably the most expensive.
Good hunting!
