Minimalist OZ version
The Australian app will, purportedly, only log the id's of lengthy close contacts, and not locations. The data will stay on the phone for 21 days before being deleted. It is only uploaded, by permission, if an app user is diagnosed as positive. Then all stored contacts can be traced and checked for the virus.
There are several issues, one being that the uploaded data will be stored by Amazon, another that the data and key will be stored together, a bit like putting your door key under a flowerpot.
The govt has promised to publish the source code, I suspect somewhat redacted, but has yet to do so. The app is a bit buggy, especially the Apple version, and the Android one needs Android 6 or better, not the "all Android" that was promised.