This is a website from Sheffield University which is looking into touch screen applications for dementia users.
There is a number of recommended apps.
There is also a forum, which I have joined, to communicate with the researchers, as it only had two messages in it. I doubled the number of messages about apps by listing the two apps I have been looking at and tested with my wife Elly who has dementia.
I would ask other drop-in users to use the site and make suggestions as to how apps could be developed.
Most commercial apps include distracting adds which take over and confuse the user. They also include in-app purchases which can cost and confuse the user. I know they have to make money, but a simple purchase up front or free would be the better options for dementia users.