Here is another handheld printer that you can use to write on any surface, including your skin. The EVEBOT PrintPen can print on paper, ceramics, glass, metal, wood, leather, skin, and everything in between. The companion app lets you upload text and images.
You get 4 types of ink and 2 types of ink cartridges to choose from. The device works with iOS/Android phones and lasts 2000 prints per charge.