I can't say that I'm all that excited about this recent update, but hey, trying new things is fun.
Slowly but surely I'm trying to wean my friends and family off texting me. I rarely use it myself to send messages, and as I've said in the past I don't like non-synced items. If I can't get my text messages on my computer or another device, then it's useless to me. I'm harsh... and abnormal apparently.
But one of the methods folks have started to use with me Facebook Messenger; and it's latest update is to now allow you to doodle on a photo when you send it through there.
Just load up the messenger, jump into a conversation (or start one) and choose to add a picture. You'll then get an option to just send (looks like a paper airplane) or the edit (pen).
You can just tap anywhere to type, or tap on the tab for the pen and change the colour by the slider on the right and change away.