Several people here seem to make a living making what seem like relatively small, simple things - bottle openers, multi-tools, key-chains, etc. Take a look at Kickstarter and see what other people are doing. It ranges from almost trivial, to surprisingly complex, and people seem to have little trouble finding funding for all of them provided they are unique, and have broad enough appeal.

I manufacture power drawbars and automatic toolchangers on my machines. In the past I've done accessories for classic Jaguar cars.

Regards,
Ray L.