The technology is available then. I just need to persuade NHS Wales to use it!
The problem is that the systems are chosen by GP practices, who are largely independent partnerships and not really part of the NHS at all. That means that if your local practice owner is a luddite, or doesn't want to invest because they'll be out of it in 5 years and can't see the benefit, or is too small for the costs to stack up, or just plain can't be bothered, then you don't get access to the shiny new stuff.
That's one of the reasons that the billions spent on NHS IT in the 2000s didn't go as far as it should have. In terms of systems X, Y and Z it rolled out a network so they could talk to each other (sometimes), and it created a lot of the system X's. With GPs unwilling to cede control of system Z though, combined with a general unwillingness to share patient data, there was no real chance of creating a unified system. Instead a massive amount of time and money was spent banging heads against a brick wall.
Bear in mind that the appointment thing isn't wholly a systems problem. Given the length of the appointments on offer the doctors probably need a few missed appointments scattered through the day just to keep on top of their schedule. That's just creative accounting in the environment we were in, but then you start hiring efficiency bullies to make everybody feel miserable about the "waste" created by this essential safety valve. Doctors can't risk taking responsibility so they blame patients, who get a guilt trip about the completely nominal money they've just "wasted".