On the Alzheimer's Society's excellent forum Talking Point, somebody very helpfully posted this link:
Obviously a database like this is only as good as people make it by registering events. But it could serve a very valuable purpose as nearly all the activities we have ever attended would be far more effective if they could get more people along. They usually advertise extensively to very little effect. This is just one slightly different approach which could help. One would like to think that, over time, more and more people would use it and pass on the details to potential clients who may not have online access or skills.