Ddlr is a drawing app that integrates in to iMessage and with the Apple Watch, or works as a standalone app.
Doodle directly in iMessages and send your doodle as a sticker or picture.
Doodle on your Apple Watch(not required to use the app) and then send it from your phone!
Ddlr has many drawing tools to choose from:
-Freehand - Draw free form line with a finger
-Line - Straight lines by tapping or swiping
-Circle, Square - Shapes drawing with a swipe or two taps
-Curves - Swipe or tap twice to make a line then tap or swipe to bend it
-Eraser
Ddlr has infinite undos and redo.

Ddlr uses icons from icons8.