There are great helicopter tour opportunities on all the major islands. On Oahu you would tour over Waikaki Beach, Diamondhead crater and the eastern and sometimes north shore.
On Maui the feature is HaleakalaCrater , the eastern shore and Hana.
On Kuai the features are Waimea Canyon and the Napali Coast (think Jurasec Park).
On Hawaii (Big Island) the features are the two active volcanoes and the opportunity to see lava flows and lava hitting the ocean.
There are a dozen or so operators on each island . The largest, operating on all the islands, is Blue Hawaiin. Be careful, if ships are in port, many of the largest are booked solid through ship's excursions.
I did a land-based vacation in Hawaii this spring, spending time on Kauai, Maui, and the Big Island of Hawaii. I took helicopter tours on both Kauai and Hawaii. Both were spectacular. On the Big Island, the flight over the volcanos out of Hilo is wonderful. The tour that I booked there was through Paradise Helicopters. They are nice because they usually fly the little 4 seater Hughes 500s...meaning everyone has a window seat. On Kauai, I flew with Interisland out of Port Allen. This is a spectacular flight, also in the Hughes 500s. They are closer to the coast and Waimea Canyon than the other operators that fly out of Lihue so you spend more time flying over the really spectacular NaPali Coast and Waimea Canyon and less time flying over less scenic areas. Now their flights are not for the faint of heart...they fly with the doors off. They are perfectly safe and really more the same kind of rush that you have cruising along in a convertible. . Here's a link to my website photo gallery with my Hawaii photos. Both the Big Island album and the Kauai album have photos taken while on helicopter tour. http://www.shutterfreaks.com/gallery2/lgyee