That looks like one of the various USB monitor tools, indeed.
As documented since August through USB descriptor dumps, the communication is based on USB HID, and therefore driver-less. It's relatively slow, due to delays on the calculator side, aimed at trying to avoid overwhelming Windows' crappy USB HID stack.
USB dumps made while the HP Connectivity Kit is running show that above HID, there's a protocol containing operations (and metadata, if that applies) for:
* sending files;
* receiving files;
* receiving backups;
* receiving screenshots;
* getting undecoded information about the calculator, including firmware version;
* setting the calculator's time;
* triggering some form of "ready" check, or something like that;
More things might be possible, but are undetermined yet, for instance (those are operations available on some, or all, TI graphing calculators):
* quickly getting the list of files without triggering a lengthy full backup ("dirlist", an very important operation - IMO, if HP hasn't implemented it yet, they should do it !);
* sending keypresses;
* remote file operations (delete, rename, maybe even calculator-side copy).
Reverse-engineering and backend implementation work for a FLOSS third-party Prime connectivity kit aimed at Windows, Linux and MacOS X, is well underway in the traditionally TI community (TI-Planet, Omnimaga, Cemetech) since nearly a month ago. Tim Wessman needs to be thanked once more for publicly helping with the peculiarities of CRC computations and screenshots on the Prime.
The current state of the code base is that:
* on the plus side, the aforementioned operations usually work, for my several beta-testers. The architecture and API are derived from the time-proven libti* architecture, and is likely to apply to the 39gII as well, which is closer to the Prime than, say, a TI-85 is to a Nspire;
* on the minus side, there's no post-processing of screenshots so that they have proper colors... and most of all, there's no GUI...
From the POV of most end users, lack of a GUI makes the program worthless. That's why libhpcalcs wasn't announced outside of the traditionally TI community yet. I don't know how people here would react to working, but arguably hard to use for a significant portion of the target user base, code... therefore, as a newcomer, better staying quiet than spamming people with my programs too early, or so I think :)
Without the video linked by CompSystems, and the implied possible work duplication (a shame in a community !), I still wouldn't have mentioned libhpcalcs here for another little while. People are of course welcome to try and use it, and contribute to it.
(oh, that was a lengthy post)
Edited: 16 Nov 2013, 3:31 p.m.