BuddyPress.org

Definitely do Option 2. Use that kind of line inside of a function that will then be hooked something like this:

add_action( 'bp_activity_add', 'my_custom_activity_meta_stuff', 10, 1 )

If you then want to allow filtering by genre, you’ll have to add an option to the dropdown at this action: bp_activity_filter_options

I can’t tell just by glancing at the code – will additional filters then be handled automatically by bp-default’s ajax.php and global.js?