Ways to sense emotions

I was afraid of which kind of software or hardware to use to capture emotion. I thought it would be expensive or hard to get. But actually not! The artist that I saw in eyebeam used Neurosky, and when I checked online, it was $200, which is payable. I think I should also get that.

But the problem is that it only give an information of stressfulness and relaxation, which is not a diverse range of emotion.

When I searched online, there were several other ways to capture emotion, such as speech recognition, ECG, which is detecting heart beat and stuffs like that, and also Galvanic Skin response. It also seemed like to capture emotion, more than one kind of sensors were needed.

There are also DIY websites of how to make cheap sensors, but I am quite afraid to make it. What if I make a mistake and shock the users! What if it looks scary, not user friendly! I should see and try more. There are forums and communities, which helps people to go and do something. I also want to know how for humans to communicate with plants.