Drylab Viewer on iPad and iPhone lets you easily share a frame, with both drawings, text, metadata and other annotations. You can send or store it using any app on your device with sharing support. This includes e.g. Mail, Messages and WhatsApp.
First: Choose your clip, scrub to the frame you want, and tap the share button:
Then choose how to share, e.g. using Mail:
Tap and hold the image, and tap Markup:
You can now draw on the frame using your finger, Apple Pencil or other stylus:
Tap Done when finished. You can now send your message.