Phone gadget to detect covid19 upcoming

Here's a 2019 overview paper on virus-detecting biosensors: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6627152/

It seems some of them are promising, and I'd be very happy to hear from someone who works in this area who can offer an assessment.

I have no idea why the sensor would connect to a phone, though. Just a power source?