If so, how do the amenities compare to parks on the mainland? What type of sites are available?

Are there any outfitters there who rent camping gear to tourists?

We'd like to spend about a month in Hawaii visiting various islands, and were thinking we could save a ton of money by making it a camping vacation. I'm having trouble finding good info about camping possibilities there, which is perhaps my first clue a camping vacation might not be the best idea.

Any info appreciated.