
Batteries
Said it before and I'll say it again.
We've got to a point with consumer tech where what you had 2, 3, 4 years ago from a technological perspective is perfectly adequate. I have a new iPhone 14 but it's not as though it's light years ahead of the iPhone XR I had 4 years ago in terms of its capabilities. Not in any meaningful way for sure.
Pretty much the only reason I've upgraded iPhones is because of the batteries not holding their charge, and the frankly dubious options for replacing them.
Consider a company that could provide
1. A high lifespan, very long lasting battery for their devices (whatever they may be)
2. The ability to easily (end consumer can do it themselves) swap out the battery with a replacement, if necessary.
Same goes for electric cars. The majority of the car is absolutely fine. It's _the battery_ that's going to be the hassle.
To me the next line of highly succesful tech will be whoever gets power sorted in some way which isn't currently being addressed. I don't know what that may involve but I'm guessing if it became an issue consumers didn't need to care about whoever tackles that will do very nicely indeed.