The iOS equivalent would be Shortcuts, which, while not as powerful as Tasker depending on the context, is an official Apple feature that most apps support. Claude and ChatGPT both have various Shortcuts hooks, including voice conversation.
The experience of having to tell Siri to "Ask ChatGPT <about something>" really sucks, though. It doesn't consistently do it, the handoff frequently just stalls out and you never get a response, the transcription that gets passed to ChatGPT is low quality, etc.
And though I have the feature enabled that should cause it to ask ChatGPT about things it can't answer, that works even less frequently.
But even if all of these things were true, the stuff on your phone you would expect to be exposed to the model as available tool calls, are not. So their efficacy is very limited.
The experience of having to tell Siri to "Ask ChatGPT <about something>" really sucks, though. It doesn't consistently do it, the handoff frequently just stalls out and you never get a response, the transcription that gets passed to ChatGPT is low quality, etc.
And though I have the feature enabled that should cause it to ask ChatGPT about things it can't answer, that works even less frequently.
But even if all of these things were true, the stuff on your phone you would expect to be exposed to the model as available tool calls, are not. So their efficacy is very limited.
(edit: iPhone 16 Pro Max, if anyone is curious)