When this gets really interesting, this is the most fun CollaborativeHypermedium. Well, hyper probably in a different sense.
Also see the related ParaLanguage.
Would be quite interesting if you can document the body language. For instance, I remember that pupil dilatation is related to if you like the person you are talking to.
I added "consciously". Most people can unconsciously "read" body language, in that if Alice produces some of the standard flirtatious body signals, Bob will get the impression that Alice might be attracted to him. However, Bob will probably not have any understanding as to why he thinks that, unless he's taken lessons in reading body language. --MartinHarper