How do we create a chatter group for a custom object. In that group I want to post feed comments and feed posts regarding to that particular custom object and display in that group.
I believe chatter groups can't be specific to an object or record only. One possible way to achieve this could be via Apex triggers i.e.
- Create a private group via apex or manually
- Make required users follow the group programmatically based on your biz rules.
- Trigger on FeedItem or specific object to programmatically post/share object required updates on the group
An option you might want to look into: http://appexchange.salesforce.com/listingDetail?listingId=a0N30000008atj9EAA
This is a bit more general that creates a group for an "Alert" vs a specific object. The principle is similar.