A short-distance walkie-talkie for use inside a noisy bar. We can talk to each other right across the room. There are many other applications. It’s clearly just a fun toy but it could be very cool. A software-only solution that might work goes as follows: Using a pair of smartphones and bluetooth headsets, the two phones could use low-power bluetooth to transmit voice between the two. If that approach can be made to work technically, then the further details of the user interface are quite soluble.