(since those microseconds really count...)
Quite some time ago, a gent named Bobo posted a small executable "gps-time" to grab GPS time from serial. I have it somewhere and planned on testing once I get a spare GPS/cable.
Also, looks like there's a Debian ARM
package available for both NTP and a client ntpdate program.
I don't even have a developer image on my new player now. I have just been focused on cleaning up tags (done) and loading music. Figured I'd delve the depths of Hijack on the occasion of the next 2.x release. What I see doing, though, is having ntpdate run at "home" startup and Bobo's gps-time at "car" startup. Optionally, you could run the NTP daemon itself and have it continually get time from attached GPS set up as local GPS/NMEA clock. Having Emplode synch would be great for simplicity's sake; also, it would re-synch during long periods (in my scenario) where NTP might not be running (I haven't looked at Hijack and other things enough to understand whether I could cron an ntpdate execution, say, every night at 2 AM)
Since GPS setting would be through plain 1 pulse-per-second signal (and Empeg doesn't have any super-duper harmonizing internal clock SFAIK), then GPS/NTP I think would be in the same ballpark, accuracy-wise. But both would be just fine!
For my car, I was initially thinking about using the covert GPS/Cell antenna listed
here along with a receiver like a Motorola Encore, but now I'm leaning toward
this small Point2Point , all-in-one unit ($179)