I think kit taught jem how to use a cellphone, more specifically how to record videos and take pictures and jem became obsessed with it. he snapped pictures and took random videos and kit think he's just having fun but jem tells them he would've loved to have something like this back in 1878 so he could now remember everyone's voices and just how they looked, and doesn't want kit and mina to suffer the same as tessa and him when they're both gone

















