NfkDumpling Bluetooth technology, unlike GPS, doesn't locate your precise destination. The app will only ask you for the first part of your postcode. All the time you are negative for Covid-19, you will just communicate with other app users. However, as soon as you say that you have symptoms, you will be asked for further details and the information will be sent to a central database.
There are two main dangers from a data protection point of view:
1 The technology could be used in the future for other purposes.
2 Even though it's anonymous, the data will be analysed and will provide valuable information, if millions of people are involved. For example, it will provide information about how many people in specific areas within specific age groups needed ventilators.
That sounds quite harmless, but it's actually worth a fortune and marketing people will pay huge amounts of money for it. For example, a company wanting to sell oxygen masks would know where the greatest need is and could place advertisements strategically, either physically or online.
Warner's company has been paid £250,000 for the app, but he stands to make much more in the future from selling the information and, possibly, using the technology for other purposes.
PS. My daughter works for the ICO and they are very concerned about the potential for hacking and misuse of the data.