Downloaded it dutifully when it came out, have used to check into places. We went into tier 4 before Christmas, so I've had no close encounters, with anyone, for some time since the only places I've been going are outdoors for walks well away from others, or to the shop for food. One person I know has had Covid back in November (he's fine now) and the only other people I've been anywhere near are close family - again, outdoors and only for a few minutes when dropping/ receiving presents at significant distance. My family is not huge, and none of them have either been tested for Covid or had any symptoms. On Christmas Day we had my immediate family, all members of my existing household, plus one other person (a friend who is in a bubble with us, who likewise hasn't seen anyone for months and gets checked anyway because she works for the NHS - from home as it's an admin role).
Clearly I've not been going to pubs, restaurants or anywhere else as they're all closed. Ds broke up from school on 18th and we've had just one notification from them of a possible case which was subsequently confirmed to have been negative.
Yesterday I got an alert telling me to isolate for 5 days.
Aibu to think that whatever algorithm it uses must have the risk bar set particularly low. I'm going stir crazy at home and cannot now even go out for a walk for another 4 days.