It would be really nice to have an API endpoint to provide 'App Objects' (defined by their client id, with all the relevant info, as set by the developer) in the App.net directory. Set in their current categories. Or filtered by category.
I have a few ideas which could benefit everyone if it existed.
Nothing concrete in terms of timeframe right now, but yes, I'm planning on doing this soon. Will almost certainly be limited to apps in the directory, as you say. I also intend to add a lot more data to help apps interoperate.