You can now use Siri and Shortcuts with an iPhone or iPad on the ChatGPT iOS app.
How do use Siri with the ChatGPT iOS app?
Simply trigger Siri (by using the Home button or saying "Hi Siri") and then... either, "Ask ChatGPT", "Send a question to ChatGPT", "Query ChatGPT", or "Tell ChatGPT" to ask a question to the ChatGPT iOS app.
How do I use Shortcuts with the ChatGPT iOS app?
See Apple's Shortcuts guide for details on working with Shortcuts.
Example
Below is a demo example made on an iPad using a combination of the ChatGPT iOS app + talking to Siri to ask ChatGPT a question + use a Shortcut to summarize a prompt output as a haiku:
Siri: Ask Siri your question -> your question is converted to your prompt in ChatGPT -> ChatGPT responds:
Copy/paste the entire response generated by ChatGPT to your clipboard (you can copy/paste any text here it doesn't have to be text from ChatGPT):
Shortcut: Let's say we want to summarize any text, in the clipboard. We'll use a Shortcut that starts a new ChatGPT conversation with the inputs: the text copied from the clipboard + the added text, "Summarize the text above please in the form of a haiku."
The response will be added in the result of the Shortcut: