There is currently an “Ask NHS” app developed by by Sensely. It has been found that by supplying merely a DOB / Surname and postcode, anyone can create an account and be given details of the patients GP Practice. For example you can find out any of the above from various public websites.
Concerns have been raised with the app developer that such publicly available data should not be the sole data used to verify an identity and gain access to information. They have thus suspended being able to use this app to book appointment etc.
Until a second layer of security is added, it is not recommend that you use of this app.