Heh, I don't get it - too techy. Though it sound impressive 
Is that feature added to the NXT coins, or is it a new core with new chain?
What is a use-case of this connection thing?
It's a modification of the NRS code base, where you can hook in "listeners" of events. And I agree with you, this is a techy thingie.
For example, let's say you are the developer for an exchange that use NXT and you want to know when a new transaction comes in to show it to your customer on your site.
Today you'll have to poll the NRS client, asking it every 10-20 seconds with the "getUnconfirmedTransactions" api function, and filtering out transactions that you already know about.
With NXT PLUS you can subscribe to the "addedUnconfirmedTransactions" event and the NRS code will, in real time let your code know that a new unconfirmed transaction has arrived.
There's lots of technical advantages with the second approach:
- You can show the transaction on your site in real time, instead of having to wait x seconds until your next poll.
- Not as complex code for you to write when you know that the transaction you recieve is indeed a new transaction and thus no special handling is required.
The big benefit comes in when you need to handle blocks, forks, knowing what transactions that got included in the new chain, etc. Those technical advantages you got from using NXT PLUS is really helping you out then.
PS. I have nothing to do with this project, I just found out about it yesterday, but these are the advantages I see.