Contact tracing, the process by which health authorities can identify those at risk of infection by virtue of proximity to a known case of a virus, has long been a pillar of pandemic response. With radio-enabled mobile devices now globally ubiquitous, it comes as little surprise to see that they are playing a role in the evolution of contact tracing methods.

Contact tracing is only as effective as its scale. The ability to evaluate only small proportions of an at-risk population will ultimately undermine any contact tracing system, manual or digital. As early attempts to develop contact tracing apps launched around the globe, technical limitations, privacy concerns and poor assumptions about adoption rates undermined almost all efforts. Into this mess stepped Apple and Google, together responsible for the software, and to a lesser extent hardware, which power the majority of our mobile devices.