In order to get out of lock down the government will want to put in place a system of tracking and testing for the presence of the virus, to ensure those with it self isolate to stop the spread. They will doubtless want to follow WHO advice on these matters.
The WHO proposes that a country combines technology with people driven systems. Technology can help, but not everyone has smartphones and not all smartphone users will want to download the app. Some who do will get flat batteries or forget to switch on from time to time.
In practice any system relies on people in the country to identify symptoms and self isolate if there is good reason to think they have the virus. They should now have access to tests so they can find out more quickly than 14 days if they need to continue with their self isolation.
It means a person who does have a test and tests positive for the virus also needs to co-operate over recent contacts. The smartphone app could help. Otherwise they need to list their contacts to the authorities who can then in turn advise those people. Even with the app there may well need to be interpretation of the contact advised by the phone, as some may not be serious or lasting contacts, or there may have been some physical separation or barrier which the phone could not see.
As we are dealing with millions of people and possibly thousands of cases, there will be many cases where judgements are made that others may disagree with. What matters is that overall, the majority of cases successfully self isolate all those with the disease and those who came into too much contact with them pending their own tests. It also rests on quick reliable and easy tests. I trust the government now has in place these measures which it says it wants, to allow a more general return to work which is vital for livelihoods and the supply of goods and services.