The PIM APIs in BlackBerry 10 are very similar to BlackBerry 7, as you still have the CRUD (create, read, update, delete) actions for Contacts, Calendar, and Messages. There is also the equivalent of “listeners” available using the Qt Signals and Slots method. This will let your app be notified of changes in the PIM databases, although your app needs to be running to receive them.
BlackBerry Hub integration currently consists of the Notification API, which lets you add a notification to the Hub with a custom title, body, sound, and invoke target. The ability to customize the icon will be available in a future OS update.
The concept of Application Menu Items has been broadly replaced by the Invocation framework, specifically the “Share” menu. You cannot add arbitrary menu items to the built in applications, but you can set your application up to handle Share (and other actions). This will make them available from those apps.