A loose definition of technology might be "the ways in which a society uses its collective knowledge and skills to produce goods and services." Or more simply, the "tools" we use to get stuff done.
Historical authors have to research the technologies in place in the time and setting of the book. Fortunately, though, those technologies are not a moving target. A millenium or two ago, people had hammers and wheels and fire--and not much else. Once the author learned what was available in the historical period, she could remain confident about writing their books based on her research.
In the 21st century, technology is exploding at such a rapid pace that a book can be outdated before it reaches bookstores. I am constantly having to decide how to refer to things, like what should I call a phone? Smartphone, mobile, cell, landline? How quickly will a term go out of use? I often use a general term, like "phone", that will likely work for many years to come.
Really, though, it's only natural for books to include technology. Since it's the way we get things done, then it's also the way our (realistic) characters do too. The trick for the author is to get real technology correct--or to get made-up technology believable.
Here are some ways that technology appears in my stories.
Whisper Falls - In Susanna's half of the story, the most cutting edge technology is the grist mill. In the US, the third patent ever issued by the US Patent Office was for a milling system. Susanna's master installs one of those systems--and it nearly ruins him financially.
I Wish - Lacey's story points out how the lack of technology can affect a family. Because they need the money, Lacey sells off their phones and computers. She has a difficult time getting homework done--because she doesn't have a laptop at home to help.
Wishing for You - Kimberley has a memory disability. This book describes all of the technology that she has to use in order to remain safe, to remember details, and to track what she's done in the past and will be doing in the future. Kimberley has become dependent on her technology, and that concerns her.
The Possibility of Somewhere - Like Lacey, Eden's family is too poor to have computers and smartphones. When Eden needs access to computers, she depends on her high schools computer lab or media center.
Fade to Us (releasing in Feb 2018) - The heroine, Brooke, is from a middle class family. Her family members have computers and phones. Her stepfather is a geospatial engineer; his business is immersed in new and expensive technologies for mapping terrain. Brooke earns income by managing websites and doing data analysis on spreadsheets of data. In this book, technology really does match its definition: it's how Brooke and her stepfather use their knowledge and skills to produce services.