The nuke alert isn't my highest priority item. In fact, its pretty far down on my priority list.
But, living in NYC, I can envision a couple of scenarios where it will help. The first is a dirty bomb. If a car blows up down the block, how are you going to know if it is a conventional explosive, or conventional explosive mixed with radioactive material?
The RadDetect I alluded to claims to have a directional feature. You can determine what direction the radioactivity is coming from and move away from it. It would also be good to have if someone decided to lace the subway platform with a highly radioactive substance without using explosives at all. I guess you could also use it to determine if you had successfully washed all the radioactive dust off of yourself. Or how radioactive your apartment is after the dust settles.
I suppose the only other time it might be of use is in the case of a nuclear plant leak. But unless you just happen to be walking by the plant (or in my case sailing by the plant they have up the Hudson River) you are probably (I hope) going to hear about it from the authorites before the radition detector goes off. That's not guaranteed though. My reserve unit was activated and I was at ground zero on September 12. On about Sept. 18, I was talking with some EPA types who were conducting air, soil, water tests. I asked them what their testing showed. They told me they were sworn to secrecy and could not say. Then they advised me to wear my respirator at all times. Early on we were all told that the TOP priority was to have the stock exchange open on Monday, and that it WILL happen. Gave me the warm tinglys knowing the government was there to help.
I agree that if a nuclear bomb goes off it isn't going to be of any use at all. You really won't need a radiation detector to know what jsut happened.
You are right to think that these things are of only limited use at best. I would not buy one if I had to decide between a radiation detector and the other more conventional PSK, BOB items.
The other thing that bothers me is that, unlike the other items in my PSK, BOB, I can't figure out how to test the damn thing without exposing myself to radiation. There is always the nagging feeling that it is a snake-oil pr scam and I am carrying around a high-tech pacifier.