Korey,
Depending on how you want it to look in the end, you have a couple of different approaches. If you are basically wanting to include this App in a Skuid page, you can iFrame it. Rob recently wrote up a pretty good response to a question concerning a different app, but the approach would be the same.
However, it sounds like what you really want to do is give the E2CP interface a skuidification. Without really getting under the hood, it’s tough to get too specific, because it depends on exactly how they’ve built their app. For instance, any triggers or workflow rules they’ve built should still fire when records are inserted/updated. If you build models on the objects, you should get this functionality automatically. From your question though, it sounds like their Visualforce page is displaying input fields / textareas that are not bound to actual Salesforce fields, with Apex Controller logic behind the scenes (which you more than likely are not able to tap into) that is doing something with this data. This makes things a little trickier.
Assuming that you can tap into the Controller logic outside of the provided Visualforce page, you may be able to write your own Trigger(s) which call the Controller methods that you need when records are inserted/updated. You would basically be trying to replicate the logic in the Controller in your own Trigger(s).
Another approach would be to try to access the Controller methods directly, and call them via your Skuid page. You’ll need to create a new Visualforce page for your Skuid version of the E2CP interface and point it to that Controller. Alternatively, you could try creating a new Controller for the Skuid page, which contains wrapper methods to get at the methods you actually need. Skuid can access any Remoting methods on this Controller, so it would take a bit of Javascript, but that may work (check out our skuid.model API docs for some help on after save actions).
Of course, all of that is pretty high level and comes with the caveat that E2CP may have put something in place that would specifically prevent you from doing any of this. They also may push an update and break it all. Still, I hope that this helps you out, or at least gets you in the right direction.
