This German invention wins the prize for the most elaborate and expensive alternative to the simple act of wiping your feet on a doormat. "Stride across this mat and moving belts of bristles brush dirt off your shoes -- without tripping you," we wrote
in April 1981. The key to the electric doormat's anti-tripping technology were belts looped over separate pulleys, alternatively mounted on counter rotating drums on each side of the mat. As we know now, the low-tech version was good enough.