This program enables you to connect a GPS module with PPS signal (or any other PPS source) to a Linux system with GPIO pins and then interface this PPS signal to NTP. This can give you very accurate timekeeping; on your local computer or maybe even multiple computers on your LAN.
When you use this program you do not need to patch the kernel to get PPS support, you also do not need to patch the NTP program.
David Taylor has an excellent description how to get it to work.
Originally this program was written for the Raspberry Pi but other systems (like the UDOO and the BeagleBone) are known to work as well.