Chirp: The App
Its is a app found on Apple App Store and the Android Market for free. You can send anything to and from another person who has the app OPEN at the time since it uses sound to detect when the other person has pushed the chirp sound and it automatically sends.
It sounds fun and really useful but everybody gets it if they have it open meaning if you send something and someone you don't know has it open they will receive it and save it. Adults could see as a safety issue but honestly what ever is on a device, its already part of the internet and can be found if you're skilled.