Good news, Apple and Google are partnering to implement system-level APIs for a privacy friendly contact tracing done via bluetooth (which, as we were discussing the other day, seems the most sensible approach):

Apple and Google will work to enable a broader Bluetooth-based contact tracing platform by building this functionality into the underlying platforms. This is a more robust solution than an API and would allow more individuals to participate, if they choose to opt in, as well as enable interaction with a broader ecosystem of apps and government health authorities. Privacy, transparency, and consent are of utmost importance in this effort, and we look forward to building this functionality in consultation with interested stakeholders.

From a draft of the spec (up here):

The Contact Tracing Bluetooth Specification does not require the user’s location; any use of location is completely optional to the schema. In any case, the user must provide their explicit consent in order for their location to be optionally used.