An intriguing location-based services: True Blue Love:

True Blue Love is a mobile phone social networking experience, designed to explore the politics behind intimate phone-based relations. Designed as a program for mobile phones; each participant enters into the program the characteristics of their ideal sexual mate, chosen from a series of preset selections. While the program is running, every time another phone comes within range, a love metric is calculated which is a representation of how close the incoming person matches the participant's ideal mate. If the match is close, the phone will emit a raucous mating call that will be unique to that participant. (...) The ridiculous sounds should function as social ice-breakers, and the unwilling couple may want to discuss what it is that they have in common that triggered the noise.