Set the router time with a GPS receiver for under $70

Has anyone tried it? Looks like I'd turn on PPS (pulse per second) in the Merlin firmware and make a USB-to-Serial cable to connect the GPS receiver to my router.

Synchronizing ntpd to a Garmin GPS 18 LVC via gpsd
http://www.rjsystems.nl/en/2100-ntpd-garmin-gps-18-lvc-gpsd.php

Enabling ntpd PPS support for Debian Lenny Linux
http://www.worldtimesolutions.com/support/ntp/Debian_Lenny_Linux_PPS_support_for_ntpd.html