WRN is 3-in-1 device for RS232 serial port was designed to solve some standard problems of a home server.

• The hardware watchdog timer
• True random number generator (based on avalanche noise)
• Low power 2.4GHz transceiver (nRF24L01+)

• The schematic and the PCB (KiCAD project)
• The firmware (AtmelStudio project)
• Linux daemon, watchdog driver and the installation for the Gentoo (Makefile)

The project depends on:

• alexcustos/RF24
• alexcustos/RF24Network

Here's an article in russian with more details:

• Part 1
• Part 2