g12u

I'd pay for a protocol or API test suite to help me build compliant clients and servers.

For example let's say I want to make my own HTTP client like curl. Instead of relying solely on the RFC or spec, I can additionally use this test suite to run my code against the spec and as many edge cases possible. I expect the HTTP product to cover the usual header grammar but also timeouts, HTTP/2 upgrades, encoding mismatch, etc.

I can see myself paying $100 and over depending on complexity.

Not sure where the scam is. At a glance it doesn't seem to be exploiting some kind of rounding bias past a threshold. It just happens to keep a strange remaining balance that you keep anyway. Nobody throws away the cards anymore because now it costs a fee to get a new one. So you end up always spending the money you put in.

A system to retrofit an appliance into a smart home.

Example: My AC has its own remote. With my device I can record the wireless signals it outputs, similar to a garage opener in a car. Then with my mobile app I can create my own interface to power on/off, set temp, etc. I now use just my smart phone to turn on my AC. I press power on the custom UI I created in the app, it will send a packet to the hardware in my LAN, and that hardware sends the matching wireless signal to the AC.

Some things might still need physical fittings and cannot always be wireless devices such as power switches. New power splitters with this functionality would also be a good way to control appliances that just need to power on and off.