As far as my (limited) understanding goes, what it will do is keep log of which phones you come into close proximity with. It will do this by identifiers being sent by Bluetooth technology and the national mobile network will not be involved. It doesn’t need to know where you are, simply which phones that you came close to. Then, if you or anybody you have been nearby to reports that they may have symptoms of the virus, a warning is flagged up to the NHS and algorithms will be used to determine which of your recent “close encounters” need to be notified.
I don’t believe the app will serve any useful purpose. It is open to abuse in two ways: some people may be reluctant to report they have symptoms and some will use it to “have a laugh” and report symptoms they haven’t got. As well as that, being a government IT project, is highly unlikely to work properly anyway. Still, it will look good. But I don’t understand the privacy concerns. Of course if you’re that concerned simply don’t download it. But there was a legal cove on the wireless this morning from Matrix Chambers (where else) suggesting that privacy concerns may see court action taken and that Human Rights implications will have to be considered. He obviously saw the ££££ sign ringing up on the till. But I cannot see how there can be privacy concerns over something you don’t have to have and which, even if you have it, does not seem to use any personal information anyway. And of course if you do develop such concerns then you can always uninstall the app at any time.