Video report by ITV Wales health correspondent James Crichton-Smith
A coronavirus contact tracing app has launched across England and Wales, with people encouraged to download it in order to help stop the spread of coronavirus and protect themselves as case numbers rise.
The rollout follows months of delays and questions about its effectiveness in the face of mixed results from other countries which have already deployed such apps.
NHS Test and Trace, which is responsible for the service, said the app was used to send alerts to users during a trial period on the Isle of Wight and in the London borough of Newham, after people had tested positive.
The latest version was piloted among residents of both areas as well as NHS volunteers from mid-August, after the first app was marred by technical issues and eventually scrapped.
As the software is voluntary, its success will also depend heavily on how many people choose to download and use it.
It will be available to those aged 16 and over, and the Welsh Government said it "forms a central part of the NHS Wales Test, Trace, Protect programme."
The launch comes as a further 389 new Covid-19 cases have been reported in Wales, bringing the total number of cases to have been confirmed to 21,548.
Two more people have also died with the virus, bringing the death toll in Wales up to 1,605.
What does the app aim to do and how does it work?
The app uses Bluetooth to keep an anonymous log of everyone you come into close contact with.
The app uses an Apple and Google-developed system, using Bluetooth to exchange randomised keys while the Bluetooth signal strength measures proximity.
If someone falls ill, they can tell the app, which will then ping their keys to a central server and in turn send them off to all app users in search of a match.
Should the system determine a person as a close contact, they will be automatically sent a notification and issued with further guidance.
The government has also said there will be QR codes to scan with the app in every restaurant or pub people visit to improve contact tracing.
Where can people download the app?
The app is available for smartphones only - not tablets, or other devices.
The handsets must have Android 6.0 (released in 2015) or iOS 13.5 (released in May 2020) and Bluetooth 4.0 or higher.
Wales’ Health Minister Vaughan Gething said: “We have worked closely with the app development team to ensure it works seamlessly across Wales and England, providing people with the right advice based on where they live.
"In Wales, the app will complement our existing contact tracing and testing services and will further support our co-ordinated response to COVID-19 at both a local and national level.
Mr Gething added: “I strongly encourage everyone in Wales to download and use the app to keep Wales safe.”
Will it protect our privacy?
The UK's previous centralised approach saw the contact matching being on a remote server managed by the NHS.
This was criticised by some as being less secure in a privacy sense, but the government argued it gave epidemiologists more access to data to better understand transmission patterns around the virus.
In contrast, the Apple/Google approach, which the new app uses, tracks the virus, not people, and uses the latest in data security technology to protect privacy.
The system generates a random ID for an individual’s device, which can be exchanged between devices via Bluetooth.
These unique random IDs regenerate frequently to add an extra layer of security and preserve anonymity.
Many other countries - including Germany, Italy, and Denmark - opted for a decentralised method developed by Apple and Google.
This makes it more secure and harder for any potential hackers to access and de-anonymise any data for nefarious means.
It also bars authorities from using the technology to collect any location data from users.
Watch: Some organisations have expressed concerns over how track-and-trace data is handled
Will it help fight the virus?
Professor Pete Fussey, from the University of Essex and Research Director of the ESRC Human Rights, Big Data and Technology Project, said the app has several hurdles in its way before it is effective.
He said: "Bluetooth can connect through walls and other partitions.
"This means people in high density accommodation have increased likelihood of being misidentified.
"These instances are also likely to occur in high density urban areas where health services are most likely to be under strain."
The app will also require large numbers of people to download it to work effectively.
Professor Fussey said low levels of adoption had been a problem for apps worldwide and added the government must detail what exactly the collected data will be used for and promise it won't be used for anything else.
He said: "The data protection impact assessment for the Isle of Wight trials demonstrated significant shortcomings and ambiguity."
He added: "In other countries, there has also been the potential to reverse identify ‘anonymised’ data."
The UK's major network operators, including Vodafone, Three, EE and O2, giffgaff, Tesco Mobile, Sky Mobile and Virgin Mobile have agreed to "zero-rate" data charges incurred by all in-app activity, meaning they will not be charged for using it.