Yes, you can build something with ChatGPT if you have a $20 subscription, and I'm sure that there are people who have already done that.

If you go that route, you do need a place to store your list that your assistant can see. For this app, it is the one and only place your task list lives, with voice input, and the UI has been tailored over many iterations, to make the common use cases as simple and as obvious as possible.

Getting an email to work the way this one does will take trial and error, because this one's not a summary, it's intentional choices, with the rationale, and it's complemented by the UI to customize your day.

Handling the prompts, as they change, will take work, and if you're using scheduled prompts, you'll need a way to know whether your new prompt works. I keep an eval set because the prompt change you make today can fail in subtle ways when looking at a different set of tasks. I've seen this nearly every time I've made a prompt change.