Users have to look into the subject's (in this case - a person) eyes for 15 seconds, while the sensors transmit the readings to the iPad app. The app then calculates from the readings whether or not the user is interested in the person they were staring at - and that's it. What both parties do after the discovering attraction is up to their discretion. BrainKiss is being demonstrated at the Tokyo Game Show this year, so if you happen to be there, you can give it a shot.
source:Ubergizmo