There is a Vtiger Twitter Connector in Vtiger On Demand. I think it has been in place for a while now but it is more prominent in Vtiger 7. You can see from the screen shot below that it is a listing of your posts and likes in twitter. Maybe I am missing something but there is no integration that I can see. It does not show you posts from a contact on their Vtiger contact record. I think I would prefer to just open twitter in a new browser page o, as I typically do, open a social media aggregator site like hootsuite.com when I want to see a list of relevant posts. So I don’t get it. Let me know if you do.
I should note that I don’t think the probability is high that the Twitter Connector will make it into Vtiger Open Source.