Re: As far as I can tell, Northern Ireland is part of the UK....
The Irish app is rather good. It looks attractive, gives useful information and it is decentralized. You can however opt in if you want to be called by the HSE if you came into contact with someone who has covid.
About the only glitch its suffered recently is that it uses Apple / Google provided bluetooth services that track proximity and the Google service went a bit insane last week and started draining phone batteries. Not the Covid app's fault, but it got the blame because Google's service went haywire.
Biting the hand that feeds IT
