IR blaster for smartphones. I still have one on mine and I can use it for tons of stuff, not just as a TV remote.
I even worked for a company who made lots of IR based products (taps/faucets, accessibility stuff) and it was amazing how many people had to buy the dedicated remotes for these products for extra money.
When I asked them if their phone has an IR blaster, so they could just download a free app and use it instead. “I have an iPhone” was the most common answer.