Any hints on how to even begin looking into this? There's a plethora of content on starting SaaS projects but can't say I've ever come across any for hardware.
That's gonna depend on your skills and what you think is interesting to pursue. Generally speaking you'll want to learn how to, at a minimum, model stuff and 3d print it, and how to design PCBs. I strongly suggest FreeCAD and KiCad for those tasks respectively.
