- Facebook make an update to Twitter
First, find your status RSS feed on Facebook. It is buried. To find it, we need to visit our profile and on our mini-feed select "See All". On the right you will see a list of items, select “status stories” and finally below this a feed link can be found. Finally add your newly found status RSS feed to the TwitterFeed service. In this step, we can set our update frequentcy, prefixed it with "From Facebook..." and am publishing just the title from the status feed.
- Twitter make an update to Facebook
The official Twitter Facebook app (found here: http://apps.facebook.com/twitter/) has an option after you install it to update your Facebook status with your latest tweet. We need to understand that there is a delay if you use twitter frequently. But overall it's really powerfull to make frequently update for both with one update in a side.
Both Facebook and Twitter have pretty extensive APIs that you can develop applications against. With these a lot is certainly possible, but it would take development time and effort to write the code necessary to accomplish whatever else you might want to do. Also keep in mind that "everything" isn't possible. The APIs are limited in certain respects, specially where privacy, technical, or other issues might be involved.