Here is an interesting case in how a new product can attract both parts with the same service but with the opposite purpose. It started as an anti-teen device:

The creators of a pioneering device that uses high-frequency sound to stop teenagers congregating outside shops, schools and railway stations reacted angrily today to news that the government-appointed Children’s Commissioner wants to see it banned. Timesonline.co.uk

But it ended as new business for ring tones:

A ring tone teachers & parents can’t hear! A tone outside the audible range of hearing of most people over 30. This means that you can get phone calls and receive text messages in class or school without teachers hearing it. Freemosquitoringtones.org