Hmm, would it make sense to create a custom library for preferences activities and does B4A support creating libraries which implement other activity types?
I'm just starting a new project and a preferences activity would make saving settings very easy. So perhaps I will first start to implement this library.
B4A currently just does not support creating activities with libraries and as Erel said I think it would be very difficult.
The best thing would be a new module type "preferences activity" in B4A IDE. Perhaps Erel will have a look into it in the future. I think it won't be too hard to implement preferences activities directly into B4A.