Whenever you try to fix one problem,you inevitably create another.How would the airlines cope with the economic effects of all the delays that are bound to occur as a result of nuisance/false warnings.Furthermore,would the airlines have to pay for it?If they do,that cost gets passed onto the customer.
We have seen since 911 several situations which on the face of it posed a threat but subsequently turned out to be benign.We still rely on human intervention which is 100% adaptable;if the circumstances change,the response changes.Would a computer instigate defcon 1 measures for a passsenger with unknown mental problems or a disgruntled first class passenger who has had one too many?Once the threat has been established as benign,how can one be sure that the pilots can regain control?That brilliant scene from 2001 where HAL is disabled springs to mind.
In an ongoing dynamic situation,computers must never replace human intelligence.The new door with correct procedures backed up sky marshalls is the best we have for now.Sounds like some of these new proposals might do some good if limited to check-in and boarding only.