Can tell when you're within 6' of an infected person? Skeptical.
Both types use Bluetooth to detect other nearby phones also running the software. Thus, when someone catches the coronavirus, people can be warned if their phone was within 6ft of that patient's phone for more than a few minutes.
I'm somewhat skeptical of this, considering how our neighbours sometimes used to feed their music through our Bluetooth enabled TV soundbar (until I took it out of service!). Sure you can get an idea of distance from signal strength, but that's not going to be particularly accurate - depending on chipset, obstructions, reflections, antenna orientation, etc. Could a Bluetooth type system suggest that I might be infected simply because it's picking up my neighbour's phone from next door, even though we never get within several metres of each other outside (only an example - hopefully my neighbours are actually fit and healthy)?
From the Bluetooth consortium's own recommendations:
RSSI is Different for Different Radio Circuits
You may notice the variation of the RSSI value even on a fixed location or distance. One factor for the variation could be the hardware/radio platforms. For instance, on iOS devices where there aren’t many different chipsets, the RSSI value could accurately reflect the relationship to the distance. The RSSI value from iPhone A probably means the same strength value on an iPhone B. However, on Android devices where we have a large variation of devices and chipsets, the absolute value of RSSI won’t help you easily map to a location. The same RSSI value on two different Android phones with two different chipsets may mean two different signal strengths. However, the RSSI value could still be very helpful in the proximity applications if you use it to get the trend of the RSSI value change. That trend could give you meaningful data.
How Can I Use RSSI in a Proximity Aapplication?
Avoid using the absolute value of the RSSI—use the trend instead
Based on the fluctuation of radio signals, we can get a fairly accurate result of the RSSI trending. We can easily know if the signal is getting stronger or weaker, therefore, we will know if we are moving towards or away from the source. Even better, if we understand the specific mapping between the RSSI and the location of the specific receiving device, we could have a fairly accurate estimate of the distance.
Sure, you could use Bluetooth to tell if you moving towards or away from an infected person's phone, but I doubt that it would accurately tell you that you're 2 metres away.