When Klingon Intelligence sent a covert strike force to Deep Space 9 to conduct surveillance operations on a group of Romulans visiting the station, they used a device manufactured on this planet to turn a replicator into a transporter for beaming surveillance equipment in the Romulan quarters. (DS9: "Visionary")
Background information Edit
This planet was only mentioned in dialogue.
"DAV-los" was the pronunciation for this planet's name from the script pronunciation guide. 
According to Star Trek: Star Charts (pp. 62, 64) and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), the Davlos (Nu Tauri) system was located in the Beta Quadrant. The system's primary was an A-class star.
According to StarTrek.com, Davlos III was an independent planet.