The new "group grope" method of smuggling a device onto an airliner could certainly employ a binary technique. There are many things that could be carried aboard that are harmless when taken individually. There are probably things that are not harmless that are not on the screening list. A plastic bottle of liquid can be left in the pockets of your pants and never set off the magnetometer.
Thanks for the validation. It would need to be something that they are immune to, or trained to work in, wouldn't it?