Maui County Exposure Notification Application Requirement Effective January 19, 2021
Introduction
Maui County now requires that visitors testing negative have an "exposure notification application" installed and enabled on mobile devices carried by travelers 18 and older.
Reference
First: the text of the requirement is in section d of rule 12 on page 12 (of 28) in the document PUBLIC HEALTH EMERGENCY RULES, EFFECTIVE JANUARY 19, 2021.
For iPhone users
Apple has chosen to make "Exposure Notifications" part of the iPhone iOS (Apple released iOS 12.5.1 for models iPhone 6 and older so they would have this feature built-in, too). Open the "Settings" app then scroll down about a page to the section leading off with "General". On my iPhone, the 9th item in that section, between "Emergency SOS" and "Battery", is "Exposure Notifications" (it seems to helpfully have a icon vaguely similar to the popular illustration of the Coronavirus). You will need to show that you have enabled this feature to leave the Kahului airport (and enter Maui County).
For Android users
(I have never used an Android phone so this paragraph is parroted from other sources.) Android phone users will need to install the "AlohaSafe Alert application or another Google-Apple Exposure Notification System application". Given the inconsistent bandwidth available via the cell network and WiFi at the Kahului airport, installation prior to departure is probably a good idea.
Download link (for the Hawai'i State Department of Health app)
https://www.alohasafealert.org/
Unnecessary remarks - please skip
If the phrase "section d of Rule 12 on page 12 (of 28)" did not get your attention, then read no further. We are assured that these Google-approved and Apple-provided apps protect privacy. While I suspect that turning off your phone, disabling the app, or disabling bluetooth can be noticed by the authorities, as I read the PHE Rules (amended), there is no requirement to carry your "exposure notification application" enabled phone with you rather than leaving it in the condo or car (appropriately hidden, of course). Individuals may have different levels of discomfort with being out of touch versus carrying a device with an active "exposure notification application".