There's already a "COVID-19 Exposure Notification" in the Settings>Google menu on my Android. AFAIK the same exists on Apple. I'm at a loss as to why they don't just say in the daily briefing "turn it on please". Develop what you want in the meantime, but it'd go a long way towards something.
EDIT: missed it had to be turned on... Thanks for the replies. Fingers crossed we get something that uses it ASAP.