Wouldn't it have been nice for Charlotte to have some of the conveniences we use today! She might never have become trapped on a pirate ship, or at least might have been able to get off much more quickly.
I imagine that if Charlotte had a cell phone (and was near enough to a signal tower) she would have been able to call her family and explain that the ship she had been sent on was unsafe. Better yet, if she had a smart phone with internet access, she could have sent an email or even used live video chat.
In more specific circumstances of the story, Charlotte might have liked to have a flashlight for navigating the dark bowels of the ship as well as the nighttime deck. Depending on whether or not you consider medicine a tool, I am sure that some anti-nausea medication would have been most welcome when Charlotte was suffering from sea-sickness.
Imagine how different this story could have been if it took place today!