Fiji is considered very low risk for travelers

https://www.cdc.gov/coronavirus/2019-ncov/travelers/map-and-travel-notices.html#travel-4

Yes, Fiji has a contact tracing ap. All travelers arriving into Fiji are required to download the ap.

https://carefiji.digitalfiji.gov.fj/

The nearest hospital to Turtle Island is Nadi (25 min in helicopter). Suva Private hospital (50 min in helicopter)

Unfortunately, it has not been proven that the sun or heat slows the spread of Covid 19. However, there is no Covid in Fiji