That's a common way of doing high precision time sync, yes. It's slightly out of phone budget/form factor, but that's what a GPSDO does. The receiver in your p

That's a common way of doing high precision time sync, yes. It's slightly out of phone budget/form factor, but that's what a GPSDO does. The receiver in your phone also needs pretty good short term stability to track the signal for all of the higher processing. It'd be absolutely fine to depend on PPS output with seconds or minutes between measurements.