I've added a camera to my Pak-O-Bird using a cheap borescope. It connects to my Android phone (Android 4 or higher) and lets me see what's going on in the Pak as I walk with her.
I made a small bracket out of the same material as the grab bar so that I could securely stick the borescope through one of the unused grommet holes. Here's 3 pics showing the installation
And here's the video. While walking outside I couldn't really tell how she was sitting but looking at the video it's clear that she has squatted down and pushed her backside up against the back of the Pak which seems to provide her some pretty good support.
Here's the borescope, 5.5mm Android Borescope, different lengths available.
And the video of Nike in the Pak out for a walk