This is a fascinating technique used to predict past, present and future of a person. Typically a Naadi reader takes the thumb impression of a person who wants reading and search a volume of palm leaves matching the thumb and makes predictions. Those leaves are said to be written by maharishis like Agasthiyar, brihu etc., Originally found at vaitheeswaran koil near chidambaram district of tamilnadu.
Unlike horoscope reading of traditional astrology naadi can make pinpoint predictions like name of father mother, wife etc.,
I will write more on this subject in my astrology blog Astrolgoy AtoZ
You can find more on this subject in yahoo groups Naadi Astrology at Yahoo Groups