Got a chance to play around and do a little more testing this afternoon. All three of the apps I mentioned above seem to work fairly well, although some seem to see more sensors than others. This could be a configuration issue, as I admit that I haven't read the docs for any of them. Too busy pressing buttons and going "ooh, neat". ;-)
I hooked the rig up to my parent's '07 Explorer, and the interface worked just as seamlessly. A lot of sensors on that thing!
I also did a quick test to see how easily I could, in the most bare-bones way possible, just log data indiscriminately and then, still in the most bare-bones way possible, parse and view it later. Pretty easily, was the answer, which is cool. I made this fairly illegible graph, just by way of experimentation.
Digimoto seems to have some pretty nice graphing and logging options for the $45 version, if I decide to go that route, but it is nice to know that I can collect this data and munge it around without a lot of overhead. I'd like to eventually get a more robust logging setup going, where I am collecting information from OBD as well as GPS and the MPGuino and integrating it all into a single file for later use.