History
Doctor Doom wanted to get revenge on Spider-Man, who had rejected his alliance offer.[1] Wanting to find Spider-Man, Doom built the Spider-Finder, a hand-held device receiving the impulses that spiders and spider-related beings gave off. That allowed Doom to scan the whole city, looking for the strongest impulses within the range, until he could find Spider-Man even if the latter was not wearing his disguise.[1][2]
The device led Doom to the position of Spider-Man, in his civilian clothes as Peter Parker. In close vicinity, however, was Parker's classmate Eugene "Flash" Thompson, disguised as Spider-Man to play a prank on Parker. This led to Doom mistakenly believing that Thompson was the real Spider-Man. Doom easily kidnapped Thompson, releasing him only later when the Fantastic Four tracked him to his lair.[1] Doom left the spider-finder in the lair, where it apparently remained for years.[2]Notes
Item name revealed in Machines of Doom #1.