They're actually a data collector!!
Yes.
A data collector.
The Barbie doll's eyes were connected to a surveillance device, but it was not a regular camera; it was a high-end data collector.
It could collect various types of data, but Eve Thompson couldn't tell what specific data it had gathered.
Taking a closer look at the other circuits, she figured out what was happening.
The data collector was tracking her sister, so wherever her sister was in the house, the doll's eyes would follow her.
And then!
The collector needed a substantial amount of power to last all these years. It needed to recharge, so the doll was solar-powered.
It followed a straightforward principle, just like a basic floor-cleaning robot. It could move on its own, and when its power was low, it would go towards sunlight to recharge.