Like, "send a message to billybob at 6:30 pm: I will see you soon."
Hi, you could try to use
Workflow app that can do a lot of things programmatically with your iPhone. I think it is free, some times ago it was about 5 euros (I think, but not sure, that this app was purchased by Apple some times ago). You could ask about how to program your task with Workflow at
https://www.reddit.com/r/workflow/ (to execute your task at a certain time maybe you should install some other specific apps like, for example,
IFTTT).
I'm not an expert about Workflow but I can tell you it is very powerful, unfortunately it is limited by iOS restrictions (for security).
An example of limitation is that you can not use Siri (in the iOS version 10.3.2) to open an iPhone home shortcut (like a Safari bookmark saved on screen of iPhone) that is a specific workflow (for example the workflow that performs your task to send a sms with specific text to someone at certain time) created with the app Workflow: for now, it is only possible to create the home shortcut of the workflow and to touch the screen of your iPhone to launch the workflow saved (it needs your fingers; only user voice is a dream for now).
Related question if someone can answer: with iPhone 5s that is not charging (in 5s Siri can't run in background without the phone being in charge) can I answer to an incoming call using my voice and Siri? That is: can Siri activates itself only when there is an incoming call and allows the user to answer saying, for example, "Hey Siri, answer in speakerphone"? After the call (call closed), Siri would switch off itself until the next call incoming. Is it possible with the version 10.3.2 of iOS with some settings?
Thanks.
Matteo