A key aspect of cooking is temperature. Whether this is checking the amount meat is cooked internally, or cooking eggs for ice cream custard so they don’t overcook, getting the temperature right is often critical.
Personally, I use a Thermapen. I’ve had one for a couple of years and wonder what I did without it. There’s a link below to the one I use, which was a bit more expensive. I’ve also added a link to a much cheaper version which some Amazon reviews suggest is pretty good, though I see some reviews questioning its longevity.
Oh, the temperature for eggs for a custard is an absolute max of 80C, about 75C cooks it nicely.
I prefer these pens to some other items. The infra-red types (there’s a link below) are great for reading the external surface temperature, but no good for sticking into a joint, or chicken, to check it’s cooked. So I’d suggest they’re not much use for cooking.
Or the cheaper item is here:
This is the infrared surface reader: