In fact it's not only and addition to mesecons, but can also be used by other mods, use your creativity!
Presenting: The minetest counterpart for real-life digital bus systems like i2c, SPI, RS232, USB, OneWire, ...
So, what is it good for?

Use case 1: Link luacontrollers together; Use them as port expanders or even create a dynamic network. For this use case, I can recommand The Tic-Tac-Toe Machine on the Mesecons Lab by Uberi which demonstrates this feature impressively.
Data is always consists of a channel and a message to be sent. See the luacontroller documentation for more information.

Use case 2: Hook up external Hardware to a luacontroller. At the moment a Real Time Clock (RTC) that gives you the current timeofday, a light sensor and an LCD display are included.
For the display, just send your text on the channel you selected when right-clicking it, in order to retrieve time or light data, send a "GET" to RTC or light sensor on the selected channel.
For developers: See the RTC, Light Sensor and LCD code to develop your own things using the digilines features.
Download
as .zip | as .tar.gz
GitHub project page
License:
- Code: LGPL
- Textues: WTFPL