How often do your seatbelt warning give out false positives? How high false rate would people accept before they removed/rigged the device?

One major reason why ignition locks that uses breathalyzers has failed to gain popularity is false positives. Police always do a blood test after a positive breath test, because those breathalyzers have know faults when it comes to a number of substances, including bread, fruit, chewing gum, vanilla extract, vinegar and energy drinks...