Last time I was in Tokyo a device for finding your ideal mate was just hitting the market. You program in what you want in an ideal mate and when you are within x number of yards it starts beeping and then the beeps get louder and closer together as you get nearer to your potential soulmate.
A far more sophositicated version is now in use on Jap 3G mobiles and there has been quite of few cases of paedos using them to trick victims into meeting them etc. I think its something that initially seems like a groovy idea but when one considers the possible sinister abuses that it could be used for on balance its a no no IMO.