CNLohr discovered that underclocking the ESP8266 wifi module's Baseband PLL made the wifi channel progressively narrower, until it could not longer be detected by an unmodified wifi receiver — but a similarly modified wifi module can detect the narrow signal, creating a s00p3r s33kr1t wifi channel; here's sourcecode (which may violate FCC Part 15 rules, so please use responsibly). (via Four Short Links)