Hawaii is considered safe by everyone’s standards. Security precautions should be followed in the areas around hotels and restaurants. Just like any city, Hawaii does have petty crimes like pick pocketing and purse snatching, but overall the islands are safe at night, as well as during the day.
The main protection you need in Hawaii is a 30 or higher SPF sunscreen, plus a hat, sunglasses and lip balm. Hawaii does have insects and mosquitoes have a tendency to be active early in the morning and late at night, so a good insect repellant might be needed on some of the islands.