This week, we have been looking at contact tracing apps using the decentralised Apple Google toolkit which the NHS in England has now adopted.
We concluded there was little evidence they were working because no country could supply data showing how many people had received alerts telling them they may have been in touch with an infected person.
We were, however, still awaiting a response from Ireland's health service. Now they have come back with some data. In the two weeks since the Covid Tracker app was launched, 91 users have received a "close contact exposure alert" - in other words, they have been told they have been in contact with another user who has tested positive for the virus and should get tested themselves.
Now there is still a lot we don't know - how many of these contacts were the kind that would not have been picked up by manual tracing, how many of them went on to test positive.
But what is interesting is that Ireland has got any data at all - Germany and Switzerland told us the nature of the decentralised system made by Apple and Google meant they could not know how well their apps were working.
"We don't know - and have no way of finding out - the number of people warned by the app," a spokesman for the Swiss health service told us.
So how does the Irish health service know that? It turns out their app invites users to give permission for the collection of some data - including whether a user receives a close contact alert.
And now people in Northern Ireland are about to get access to a similar contact tracing app made by Nearform, the company behind Ireland's Covid Tracker. Northern Ireland health officials confirmed at a briefing today that the app, to be released next week, will collect some data to show how it is functioning.
In the early days there will not be much to go on as only between 10 and 20 new cases of the virus are being reported each week, but if there is a second wave of infections in the autumn they hope to know more about what is going on.
The officials also revealed their app will work across the border, as will Ireland's Covid Tracker. If a user in Belfast travels to Dublin and is in close contact with a user of the Irish app who later tests positive for the virus, they will receive an alert even if they have returned home. This is because the two health services will share a common database of app users with positive test results.
It looks then as though Northern Ireland has come up with a world first, a contact tracing system that works across borders. At this morning's briefing officials said they were sharing what they had learned with the NHSX digital team in London. But it appears unlikely that an app will be rolled out in England for some months.