All smartphone web browsers, common tools like image galleries or download managers, and many communication apps (Twitter, Facebook, Whatsapp, etc.) offer the option to share specific content to other apps. So I can select an image from the Gallery and share it via Twitter; select a downloaded file and share it via Outlook, select a tweet and share it via WhatsApp, and so and so.
Can Flow app be one of such candidates, so we can share messages, images, files, even links from other apps into a certain Flow?
Let's take the example of bookmarking services like Instapaper. Assuming I already installed Instapaper in my smartphone, if I open an URL from the browser, I can then share the link via Instapaper; and if I previously created different categories inside Instapaper, once shared I can also select the "destination category".
In a similar way, if I select a file, an image, a message or even a link to share it, I would expect Flow app listed as one of the options, and once selected I would expect to decide which Flow to execute -only the Flows expecting such input should be displayed-.
You can see this implementation as an alternative to current Flow Buttons, even more powerful.