Actually, the effort required to do this hack is quite high...
Not it isn't.
Actually, I don't know for sure either way, but you have to be a fool to bet that it is. History has shown very consistently that security holes in any given product are always easier to exploit than the vendor will admit to, and they become less and less difficult as time passes without a proper fix.
Off hand, from the attack demo video the guy is running it off a Pi with a USB RF dongle... probably an obvious application of RTL-SDR. I suspect the biggest hurdle is that you'd need access to one of these pumps to build your attach tool.
An overdoes of insulin is indeed dangerous and can cause death if left untreated for an extended time...
You meant "underdose".
An overdose of insulin lowers blood glucose and results in hypoglycemia, which is extremely dangerous and can cause death very quickly if the diabetic happens to be doing something like, say, driving and doesn't catch the symptoms or blood sugar drops far too quickly. Being asleep would be another bad time to have glucose levels bottom out