The DigiCDC library allows the Digispark or Digispark Pro to appear to a computer as a Virtual Serial Port when connected by USB. This makes it appear just like a standard Arduino and allows the use of the Serial Monitor built into the Arduino IDE.
DigiCDC was based on the V-USB project and avrcdc project - the first version (the hard work) was created by ihsan Kehribar (http://kehribar.me) and then turned into an Arduino library and refined by Erik Kettenburg (Digistump)
The DigiCDC library is based on V-USB - because the Digispark does not have hardware USB support. This presents some unique limitations in how it works - outlined below:
Examples can be found in the Digistump Arduino release (1.5.8C or higher) under File→Examples→DigisparkCDC
DigiCDC can be used to make the Digispark appear as a Serial device to an Android device when attached to an Android device's OTG port. The device must support Serial/CDC devices via OTG
Phonegap/Cordova Plugin used in the examples above to connect to a DigiCDC device:
(plugin use FTDriver by Keisuke SUZUKI https://github.com/ksksue/FTDriver)