To show you don't have COVID-19, COVID negative test wristbands are a great option for people to easily identify that you are safe to be around. Once events have checked if you have a negative test, a wristband can be worn to prove you are allowed in the event.
This can also be done for people who have the vaccine. People can wear a COVID vaccination wristband (or vaccination id bracelet) to display they have been fully vaccinated, making them safe to be by. A vaccination proof bracelet would make admission at events very convenient since they are easily seen on the wrist.