I was talking about something much simpler than full-blown A-GPS. If we simply figured out the format of nvd_data and inserted new ephemeris from the network regularly, it seems that cold starts (3+ minutes) would become warm starts (~15 seconds as established in this thread). You don't need to talk to the chip directly as nvd_data is already fed to the chip by gpsdriver. You also don't need to know precise location. There were reports in this thread of people driving several miles and still getting a warm fix in seconds. Defaulting to last known location should work in most cases.

Here is a good experiment to try if anyone has 2 N810s.

1) Get a fix on both units so that nvd_data is initialized.
2) Wait a day
3) Get a fix on one of the units. This will take a few minutes.
4) Edit nvd_data on the second unit. Copy the B 2 section from the first unit.
5) Start GPS on the second unit.

If I am correct, the second unit should obtain a lock in about 15 seconds.