If it was based solely on the app (whoever provides it), I would have some confidence. If it is based on memory of where you have been and who you might have been near for over 15 minutes, I can see some misuse. If you have an ex-partner and wish to deny him or her access to your child, or just punish him, you could claim symptoms, force him or her to self-isolate for a period, and then report him or her if you suspect they have not done so.