In July 2011 Black diamond announced they will be releasing a new magnetically locking carabiner called the Magnetron. It uses small (neodymium?) magnets on two sliding locking arms which are released by pushing them towards the nose of the carabiner. A steel element inside the gate of the carabiner attracts the magnets to lock the gate when closed. It is due for sale in July 2012. The video from BD, with engineer Bill Bellcourt, describes it well:
Image from Black Diamond website
