What is it? This is a simple adapter which enables you to communicate with projects over RS485. The stick has an FTDI chip, micro USB port, RS485 driver, RJ45 connector, and TX, RX, and power LEDs. Another really nice feature of this stick is that it can be used to inject power into the RJ45 jack; +V on pins 4,5 and -V on pins 7,8. This is a standard "passive PoE" injection scheme, which is used in a variety of commercial equipment (http://en.wikipedia.org/wiki/Power_over_Ethernet#Passive).
Why did we make it? We created this to make prototyping our RS485-based sensor networks easier. They're a simple way to both communicate with and power a remote project. We chose the passive PoE pinout to be compatible with commercially available injectors and, of course, consistency.
RS485 is a robust signalling protocol and these sticks can be used to communicate for hundreds of feet. Even though it's easy to connect PCs together over Ethernet, it's a fun demonstration to connect two computers together with RS485 Sticks and a crossover cable to send messages between two serial terminals!
Because MicroUSB is the standard now, we find it really annoying to have to hunt for a Mini connector to use the usual FTDI breakouts. This stick and our other USB-enabled products use micro connectors for maximum convenience.