Custom fields in stream

Hi,

I was wondering if it will be possible to add custom fields to stream feeds?
For example, if you'd wish to create a group for a specific topic and would like for all posts to be formatted the same, for example:

"I am going to [city - list] on the [date - calendar], at [time]"

All fields should be searchable and filtered, no free text is allowed.

I think that can be an interesting feature that I can see a lot of use for.

BTW: is it possible to disable postings in home stream and enable only in groups - allowing only stream posting through groups and not through public/home stream (while groups postings keep updated in home stream)? couldn't find this setting anywhere...

Thanks