Side project I've been putting a lot of hours into: Ping, an Android app where phones talk directly to each other over Bluetooth — chat, GPS location, photos, even SOS broadcasts — with no Wi-Fi, no cellular, no backend server anywhere. Every phone running the app acts as a relay, so a message can hop through several other people's phones to reach someone who isn't even in range of the original sender. Started it because I kept thinking about how fragile "communication" actually is the...