High-fiber, low-sodium, eh? Try Kashi GoLean Crunch. Personally, I hate it as a cereal- I think it tastes absolutely awful in a bowl of milk- but it makes an excellent snack as well. Especially in place of something like chips or popcorn, because it's crunchy. 1 cup (a serving) has 8 grams of fiber, 7 whole grains, and 9 grams of protein.
This is literally some of the healthiest stuff you could possibly buy. I'm addicted to it now, I eat at least a cup a day with a little bit of munching on the side.