I think often the goals of contact tracing apps are misunderstood. The goal isn't to replace "name and phone number" human contact tracing, but rather to augment it. Iceland's location based approach seems to emphasise this, albeit at expense of privacy.
Where contact tracing apps help is for contact events where people are in relative proximity for sustained periods of time. It seems that prolonged contact is a major factor in spreading the virus. If you're on a train with someone for half an hour, you'd not be able to identify them through regular contact tracing, and they wouldn't be able to be altered. On an aircraft this can usually be done as the airline cooperates with public health authorities to identify those sitting near a given individual on the plane etc.
The impersonal but sustained contact situations are the ones apps can really help with, by raising the number of people able to be alerted to their risk of exposure. Traditional tracing handles people you know. App-based tracing, if it gets adopted, can help with the people you don't know but are sitting near, or otherwise around for a prolonged period.
Where contact tracing apps help is for contact events where people are in relative proximity for sustained periods of time. It seems that prolonged contact is a major factor in spreading the virus. If you're on a train with someone for half an hour, you'd not be able to identify them through regular contact tracing, and they wouldn't be able to be altered. On an aircraft this can usually be done as the airline cooperates with public health authorities to identify those sitting near a given individual on the plane etc.
The impersonal but sustained contact situations are the ones apps can really help with, by raising the number of people able to be alerted to their risk of exposure. Traditional tracing handles people you know. App-based tracing, if it gets adopted, can help with the people you don't know but are sitting near, or otherwise around for a prolonged period.