This sets a new bench-mark for state-sponsored terrorism - aka asymmetrical warfare.

Presumably, what can be done with pagers can be done with cell-phones - or any of the devices that we're all addicted to.
Imagine, at scale, a years long supply-chain of cellphones (from factories in China, for example), shipped to the US, all set to be detonated remotely, simultaneously.

Another good reason not to be hopelessly dependent on Totalitarian regimes for most of your product manufacturing.

Medicine is another weak point waiting to explode (figuratively). Plenty of dodgy characters running that industry in the west already, then massive reliance on China & India for production ...
Any type of medicine could be spiked - not necessarily the frothing at the mouth suddenly reaction, but maybe highly carcinogenic, so it's not immediately obvious it's even happening.