First there was the radar gun, and heavy-footed drivers were briefly slowed. Then came the radar detector -- a.k.a. Fuzzbuster -- and the battle of highway technology heated up. Police introduced K-band radar, which used higher- frequency signals to fool the Fuzzbusters, and "pulse" radar, which fired bursts too brief to be detected. But each new measure brought new countermeasures, including ever more sensitive detectors and systems that let speeders slow down without flashing telltale brake lights.
Now the combatants are turning to even more exotic technologies. A small Denver company called Innovisions Research has introduced a line of Stealth attachments,...