This board contains a PIC-microcontroller (PIC16F1938 to be more precise) that translates ASCII-commands received via a serial link to I/O operations on the microcontroller's port pins. The 22 pins can be used for digital I/O, ADC, capacitive sensing switch, PWM and counter.
The serial link can be established via WiFi, Bluetooth (2.0 and 4.0) or USB. The board accomodates footprints for connecting either a HC05/HC06 Bluetooth module, RN-41/42 Bluetooth, RN-171 WiFi, ESP8266 WiFi, Elektor FT331 BoB for USB, Elektor FT232R BoB (USB) or the Elektor BL600 E-BoB (Bluetooth4.0).
The author developed Java classes (libraries) for controlling this I/O board, so the user can focus on the functionality of the app rather than digging into details of handling I/O.