The Seeker Project was developed by Captain Samantha Carter. The project would recognize Goa'uld vessels on a direct course for Earth. It depended on a device being positioned on P5C-629, which is a planet within the corridor of space the Goa'uld pass to reach our Solar system.
Given the technology Earth possesses, the device would be able to detect the Goa'uld "footprint", even at hyperspace speeds. With this technology, the device could automatically dial the planet's gate and warn Earth about the incoming threat.
The Seeker Project was still in development the last time it was discussed, and was put aside to rectify a new threat on Cimmeria. (RPG: "Friends and Foes: Stargate Season Two") (SG1: "Thor's Chariot")