I've had them quite a number of times and I've been pondering how to make them myself. They're pretty costly here.. $3 for 150g at asian grocery stores (they're made by a Korean Kimchi manufacturer) or $4.50 as a full (small) salad at japanese takeaways.
I have seen some types of dried seaweed at the nearby grocery store and judging from the picture, there are those that can be made into salad.
Today, I've just had it with finely julienned cucmber and my verdict: too good for summer. I think they work well for cucmbers (an alternative to seaweed) and I hope I can get the recipe here..