Okay, people, I understand that "radiation" is this big scary thing that we don't know what to do anything about. We're not quite sure how it works, how far it can travel, and what it can do to us.
Here is your reality check - Potassium Iodine pills and such are NOT necessary, and can in fact be harmful to people with heart trouble, kidney trouble and other health issues that they may not be aware of. Potassium directly affects heart rates and rhythms, and even us EMS types are only allowed to monitor it at very low levels! If you use iodized salt, you should be fine for most anything. I mean, geez, most of us get more radiation from an x-ray!
Interestingly enough, before we had ever heard of the atom bomb or a nuclear energy plant, X-rays and fluoroscopes were the big fad. You could go to the shoe store and put your feet in a machine so they could fit your shoes and see your bunions and such without even having to remove your current footwear! http://www.museumofquackery.com/devices/shoexray.htm
The likelihood that dangerous levels of radiation will reach Hawaii, let alone the mainland US, is low. The radiation workers in Fukushima have been allowed back into the plants to continue their efforts to cool the reactors and keep us all safe. The design of these plants is different from Chernobyl's plants, and are operated according to very safe protocols (unlike the "ooh, let's see what this does" mentality that led to the Chernobyl incident).
If you simply must have something to worry about, put your energy toward something useful, like a rational plan in case of whatever natural disaster your area is prone to. And if you can, spare a thought, a prayer, a donation for the people of Japan, and remember New Zealand as well.
For my part, I am working on better living arrangements, including a garden and livestock. We have lanterns and gear for power outages, and are working on plans for self-sufficiency. If that's too much for some folks, then prep an emergency bag in case you need to leave home or be stuck at home with no power or water. Just something to think about.