I’ve been watching his channel for a long time and remember back before they were together.
If I remember correctly he first built her a wheelchair to go hiking in. That was kinda the beginning of their relationship. I think there was also a stair climbing wheelchair involved at some point, but that could have been a sponsored thing rather than something he built.
He’s also been working on an electric humvee. So he’s a lot more than just the channel where he scratches and tears apart phones.
It's explained not very far in the article what the first wheelchair he built her was.