title: make an app appear in share panel to accept selected text from other apps
body: <p>I'm writing an app in iOS which handles text. Normally users can enter in their own text via a text area but I would also users like to be able to highlight text in other apps (e.g. mail, websites etc.) and allow users to send text via selection and the share panel where my app would then appear? Can I do this in iOS and if so how? Is this like the reverse of UIActivityViewController? </p>
  
  <p><em>An example from my phone. I'm on a website, see phrase which is interesting, I select it, and then send it to Notes from the text highlighting share option. Notes is an Apple app but I could also send it to other third party apps such as Twitter or WhatsApp. I would like my app to also appear on this shared list and be able to receive and process the text.</em></p>