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I think you can push activities front and help developers to integrate it with applications by creating two new widgets:
1. SemanticListView
2. SemanticIconVIew

It should be prepared to future use and developers should use it, when he/she have allowing semantic operation to user. It should provide a way to filter and search items. Search/filter criteria should been added in future. Maybe these widgets should be modular?

How to realize this? Add two new method to these widgets: getConfigString and loadConfigString, so application could save and load settings on the fly, for example, when closes/starts. Application won't mesh with this settings - if it like to save settings in file with other settings, it should encode widget settings (in base64 for example). If you allow to separate application and widget logic by allow to obtain/load settings in string config, you can extend widget in future, when activities could be more mature. By realizing this, you could also experiment with activities.

Disadvantage: developer cannot do many things, like extend widget by own, theming it, etc. But, when widgets will be mature, you can allow this. Also, you can add api to report features application support in subclasses of this widgets, or program name and version, so you can compare it with buid-in list of features and disables some or report back to application it should disable some feature.