At the very least, a mobile app that tracks your location history over the last 2-3 weeks would be helpful. Even if the data is just stored locally, perhaps eventually overlaid onto a map for reference, that would be helpful if you test positive, because then you have a way to review it and clearly indicate where you've been when, to report to authorities that might want to contact-trace or alert communities. ("A covid case was at your local Safeway between 7:14 and 8 pm on the 23rd.")
More spruced up is something where location history is submitted through a central service so that people could be automatically informed if there's an overlap. A while back I was working on an Akka Cluster Sharding app that did something similar, but it wasn't for pandemics. It'd only be valuable if a critical mass of people were using it though, which might mean it'd have to be a government or big-corp effort.
We built a privacy focused contact tracing app. It records your location history for a 3 week period and then compares it against reports of COVID-19 infections. The comparisons happen all on your phone so your location history is not exposed.
We are working on getting into the app stores but both Google and Apple have changed their requirements requiring us to partner with an existing recognized organization. We are working as quickly as possible to find someone, if you know of any potential partner, please let me know!