you might have a viable, yet useless toy.
That's my video! And I (almost) considered actually doing that
! I work in product design, and when the owner of our partner factory in Shenzhen saw my video, he got super excited and tried to convince me that his needs to be mass produced
(He is a really fun guy, retired engineer now "business person", designs toy drones when bored). The main blocker here is the costs of the parts. I think it really needs to be that exact energy harvester and that exact cap, because of how shit the potato is as a power source. Anything else and the leakage becomes too significant. I've spent a few weekends getting this darn thing to work. Those motors run at ~20mA, and have ball bearings, so little can be optimised there. All these parts are expensive, from big brands, they add up, and it would turn out to be a pretty expensive useless toy.
On top of that, I'm guessing the observant people here might have noticed that the whole "free will, choosing where it wants to go" part is faked with an RC receiver and LiPo cell. Of course, some random movement can be implemented on a fancy ultra-low power micro, but that's more cost and development time. But then again, maybe worth a shot. I wouldn't buy this for ~$35, but maybe somebody would? Would sure love to see this making kids happy and engineer-y