Tiare makes a good hedge, but you will have to prune it some to keep it low. Mine has been easy to maintain at 3 feet tall. It depends how much sun it gets. Bouganvillea is a good choice, or hibiscus. Crotons are awesome as a hedge too!
Aloha

Koki'oke'oke'o (Hibiscus arnottianus), is a good native hedge. It has fragrant white typical Hibiscus flowers that are slightly fragrant. It does not look to flashy but it works as a hedge. It is used in commercial landscapes. However, I don't know if this species (endemic to Moloka'i and O'ahu) is available on Hawai'i. Other native Hibiscus suitable include Hibiscus kokio. I don't know of the availability of this species on the Big Island, but it is said to be native there. I don't think you would consider these plants heirloom. But they carry an original look of the Hawai'ian flora. No crazy thousands of colorful cultivars (like H. rosa-sinensis), just pure native species.

Bouganvillea, and Crotons should be alright as well. Individually, I would not consider either of these attractive plants. But they can play a role in landsacapes.

Mock orange is very commonly used, but it makes an excellent hedge and when in flower the fragrance is often carried by the wind.

I've tried mock orange in some areas, but they never seem to bloom, don't know why. Jasmine is the same way.

The koki'oke'oke'o sounds interesting although it's name is almost as difficult as humuhumunukunukuapua'a (small fish, big name). Is the koki'oke'oke'o a dense shrub or a loose one? Although, I could always pinch it back to get it denser. I'll have to look at the garden shops and see if any of them have any of this hibiscus. Can it be propagated in the usual hibiscus way of just sticking twigs in the ground and watering? Then I could buy just one and eventually have a hedge.

Many growers have grown Koki'oke'oke'o from cuttings. I personally prefer to grow them from seeds (I don't think I'm a cutting-inclined propagator). They are relativly fast growing, although growing from seed will take patience. Seed propogation of this species is quite easy. A large leaf will be about the size of a shaka (2dm), though most leaves will not reach this size. It forms a pretty "cozy" looking hedge with few or no open spaces. Its density does depend on pruning. I have seen it planted McDonald's', and gas stations. They seem to stay well maintained in commercial landscapes, and in my opinion are much more attractive then the common red hibiscus rosa sinensis.