Is there rigid insulation in the exterior walls?

I've done it - the walls are plywood covering foam insulation, so running wires in the walls is out. In some areas you can run wire down inside cabinets (say behind drawers) and up, but not many spots I've seen in my 179. I used stick-on plastic wire channel in one location, to add two reading lights on the underside of a shelf over the bed. I tapped into an existing light (make sure fuse is pulled before you cut into a line).

Yes, not the most elegant solution but it works!

You certainly could do that, they be easier to install! I didn't for a few reasons: I have not been able to find stick-on led lights that I like or that are anywhere as bright as the wired ones; each 4 watt LED that I add to the Pod only draws about .2 amps/hr, which is minimal if you have a decent deep-cycle battery system; and I live in Colorado where I can use solar panels most all of the time during camping season. 

Like most things, best in moderation; I've only added two, under the shelf above the bed, where it was easy to access wiring and most of the wiring is hidden. 

If anyone's found a good source of non-wired led lights I'd love to see them.

The counter argument was stated above, and he's right.  I don't want to light a whole room, I want specific "task lighting" as it is called.  That is a lamp contained in a shade that can be directed to a small area, like the book my wife is reading while I am sleeping next to her.

https://www.etrailer.com/RV-Lighting/Gustafson-Lighting/277-000335.html

Thanks for posting that link - wish I'd seen those before I added more of the Rpod "moonlights". You are right, they dont work very well as a reading light. I may be changing the ones I added for the reading version.

Ours are about 6 or 7 years old and have the original button cells still place.

Nice light - might look into one for my woodworking stuff! We hardly ever camp where there'a ac power so don't know if it'd work for us in the Pod, though.