Might have protected Ross Ulbricht, but he’s an edge case. Anyone had their laptop yanked away while using it?
The agents arresting him did in such a way that they prevented him from touching his laptop (by creating a diversion), because they were feared that such a protection might exist.
But that's literally the scenario this physical-separation killswitch was designed for.
He wouldn't have had to touch his laptop to trigger this. Quite the opposite.
It has no remote part, it doesn't matter how far the user is.
If you're thinking about attaching the trigger to your hand with a lanyard, the agents could easily hold your hand in place, cut the lanyard, ...
I don't understand why people always assume the FBI is brain-dead and could not use countermeasures against devices such as this if they become wide spread.
If the user is attached to the switch and moves more than 50 cm or so from their laptop, the switch is triggered.
The man was running a multi-million dollar drug marketplace in a public library.
A public library is even worse for that purpose, because of security cameras and witnesses.
Probably wouldn't work the same in Euro countries which have other plug types.
They will bridge the outlet, and take the outlet, AC adapter, and everything connected, without the AC adapter even reading a voltage drop.