Up to now, I haven't got a satisfactory answer to this question. There really was no app on the App Store which let you schedule your text messages. And no, jailbreaking is currently no option.
So, we created our own app which solves this problem: n8message
(just search the App Store for
n8message, there is also a Lite version which has no SMS credits bundled)
Yes, the app sends your messages fully automatically.
No, the app doesn't do anything that is forbidden by Apple.
Sending of E-Mails is free, but for text messages you need to buy credits. If you send a text message over my app, you're causing costs to us, so we cannot give away those text messages for free. There are, however, some ways to obtain a few credits for free, so you don't have to pay just to test the app.
The app does not yet work in all countries (due to some cell phone operators blocking messages), so currently it's available in those App Stores where it is working. For example, it does not work in the Americas, so you won't currently find it in the US or the Canadian App Stores.
Please tell us what you think about n8message, comments and feedback are very welcome.
EDIT: Here's some more explanation as to why the app does not work everywhere: When you send an SMS through n8message, we have to send the message in a way such that the receiver sees your phone number as the sender. Without that, the receiver would see something as
000 or some random number as the sender.
This is done through what's known as Dynamic Sender ID. Unfortunately, in some countries (like the United States, Canada, China, and many more) dynamic sender IDs in SMS messages are forbidden, for various reasons. The most frequently heard reason is that dynamic sender IDs can be abused for spam, harassment, or even fraud.
That's the reason why n8message currently does not work in the US, and likely won't be working in the near future.