Finn's Phone is an electronic seen a few times throughout the series. It is different from most phones, and may have been invented after the Mushroom War. It was first seen in the episode "The Pajama War", and was used for a texting feature. That text feature allows sending words, images, or videos, and possibly other thing. In "Happy Warrior", Finn uses the phone to look through pictures of Jake, until Lumpy Space Princess throws it into the Fire Kingdom.
The phone is rectangular and grey. Below the screen, there is a smaller, bluish-grey rectangle with two light grey buttons in the shape of a circle in the center. There is a scale and an antenna on top.