I've just finished my test (although I already knew this would work) and the results are in. The short version: it works!
Here's the long version, with pictures.
In the picture below, you see a Sunforce 10 amp PWM charge controller wired directly up to the battery of my tow vehicle (2005 GMC Envoy XL, 4.3L). I just used the 18 gauge wire that came with the charge controller. If I were doing this on a regular basis with this charge controller, I would use 16 gauge wire, but over a run that's less than three feet, 18 gauge is fine for this test at least. I just wrapped the wire around the battery terminals; this is a terrible electrical connection, but again, it's just a test.
In this picture, the vehicle is not running. The controller powered up as soon I connected to the battery (red light in upper left). While the controller indicated that it was maintaining a float charge on the 75 amp hour battery (barely visible on the bottom right) that I had just taken off of a wall charger. However, my voltage reading on this battery was just over 13 volts, indicating that there is no charging actually occurring.
In this picture, the vehicle is now running. The voltage reading shown on the charge controller is the same as that of the vehicle's battery, 14.08 volts. You can see that the blue charging light is now lit.
In this picture, you can see the alligator clamps from the charge controller attached to the battery and my multimeter measuring the voltage of the battery. The voltage is 13.58, .5 less than the voltage on the battery. As such, it is clear that the charge controller is charging the battery.
So why am I putting forward this method of recharging your Pod's battery when you can just use jumper cables, which certainly does work? For reasons beyond the scope of this thread, the jumper cable method is just raw current from the vehicle's battery into the Pod's battery. It is not a controlled charge because if the Pod's battery is low when the jumper cables are connected, power from the charged vehicle's battery will quickly flow at a very high rate into the Pod's battery in order to 'equalize' the charges (like two water tanks connected to each other with a pipe will naturally seek their own level). This is not good for deep cycle batteries, which are best charged from a multi-stage charger, which solar charge controllers like this one are.
For those who are dry camping (i.e. boondocking) on a regular basis with their Pod, they need to have means of charging their Pod's battery. If they aren't interested in running their air conditioner or microwave, then they don't really need a generator. Many of these people opt for solar panels to do this, which is perfectly fine. However, solar panels don't work when it's cloudy, shady, or dark. By simply connecting their charge controller up to their tow vehicle, they can recharge their Pod's battery in a controlled, healthy manner.
For those that already have solar panels, all they need for this method is a set of alligator clamps to connect their charge controller to their vehicle (these alligator clamps could be wired into a pair of MC4 connectors if that is what is already being used to connect their solar panels to their charge controller). Those that don't have solar panels can just purchase a charge controller (10-30 amps would be appropriate; I like the one in the OP that's just $18) and a set of alligator clamps to attach it to their vehicle's battery.
Honestly, as little power as we've gotten from our 100 watt solar panel in our time camping (we usually have hookups, and when we dry camp, we usually park in forests with lots of shade), I would personally not recommend that the 'occasional boondocker' bother with the expense and space of solar panels. Most vehicles can idle 1-2 hours on a gallon of gasoline, equating to $1.25-$3.00 at current prices per hour of charging. Considering that a rigid Renogy 100 watt monocrystalline panel is currently $130 plus tax, that means you could get around 45-100 hours of vehicle charging for the same price as the solar panel, and you aren't dependent on sunshine for that power.
So I consider this to be a very viable approach for either those who do occasional boondocking, can't get power from their solar panels for whatever reason, or else just need to recharge their Pod's battery but can't or don't want to do so from shore power or generator power.