So what do inventions have to do with fantasy, let alone fantasy world building?
Depending on what your story is like, you might have lots of "Old World" items in your fantasy setting. I'm currently reading a book that has people walking around lighting the lanterns in the street. There were some books I read where black powder was involved and people fired muskets. Steampunk involves, you guessed it, steam engines.
Personally, I don't have black powder in my fantasy world. This is a decision I made some time ago. I feel the invention of guns made the fight too easy. Hand to hand combat, in fantasy, feels more honorable to me. I know, contradiction in terms. But I have pirates. So how do I fire cannons on ships? I don't. They have small catapults and ballista anchored to the decks of the ships.
Catapults have a basket to launch a boulder, ballista look like giant crossbows. In my case, the catapults launch flaming pitch pots. The ballista have lengths of rope attached to the spear. Some have been soaked in pitch and they're lit as they're launched. Land a flaming rope over the deck of a ship and you have some serious destruction.
In Melanie Rawn's "Dragon Prince" series, there was a water clock that told the time of day. Items like these bring about a sense of familiarity. It also describes the progression from candles with notches marking the hour to actual clocks.
What if my cannons were steam powered? What if I came up with some other sort of combustible material that would launch projectiles at objects or armies? What other inventions could I think of to bring into my fantasy world that would be believable?
These are all questions you have to ask at the beginning of it all, before you set pen to paper or fingers to keyboard. What will you allow in your world and what do you draw the line at?