To: backhoe
"I've heard eating kelp is better than nothing, but I wouldn't bank on that, given a choice!"
Don't bank on it. From the Potassium Iodide FAQ section on Q: Is Iodized Salt, Tincture of Iodine, Water Purification Tabs, or other Iodine Sources Effective?:
Kelp Tablets...hardly. Solgar® Kelp Tablets, for example, contain only 225 MICROGRAMS of iodine! (Fortunately, it is also available in a 1000 tablet bottle, unfortunately though, you'd need to be swallowing 442 of them per day and not wander too far from a bathroom!)
I urge everyone to view the rest of the text there, it addresses everything from sea salt to water purification (iodine) tablets. The information is vital to anyone considering such things as alternatives, as the results vary from ineffective to deadly.
Possibly viable alternatives including topical application are described on the Plan "B" for anyone caught without KI or KIO3 tablets in a nuclear emergency page.