Instead of shutting off wifi, they ought to be looking at ways to detect PETN.
I don't know why the government expects the terrorists to be all James Bond-y sophisticated; the Sept 11th terrorists used their real names and box cutters, and these guy mailed their packages from Yemen.
Why would someone want to make a trigger that uses some sort of wifi trigger mechanism when a simple timer would be just as effective and less prone to failure? And the issue shouldn't be about stopping potential triggers; the issue should be about detecting the explosives.
The more we focus on higher tech issues the less we focus on the more obvious - and probably more likely - low-tech issues.