Set an alarm in your clock app, repeat forever

Yeah it's called Temu. You'll get them in your email and SMS inboxes too.

Clock app, make a 30 minute timer, reset when it goes off. Why do you need a whole app for that?

This sounds like the Pomodoro technique.... There are a lot of apps for that.

Calendar. Recurring event every 30 minutes with a notification at start.

For this kind of thing, I use Godot and write a quick and ugly one-off app. That way it works exactly how I imagine and I just send myself the APK over messenger and install it :P

Although it would be a joy to implement in hardware.

Probably called cockoo clock or pomodoro timer, or interval timer. A quick search shows there are multiple such apps, I haven't tried them so I'm not sure which to recommend.

Or... Hear me out...

Use the default built-in alarm.

Why? Most of the non-built are somewhat blocked by phone notification controls such as do-not-disturb and other similar modes. Getting an app that has its implementation of this just right can be frustrating...

Just put a bunch of 30 min interval alarm, with a slight different ringtone than your usual alarms and you'll be golden :)

You could try a ship’s bell app, there are a bunch out there. They chime every half hour

This sounds basic enough that you'd almost certainly be able to do this with Tasker. It's not FOSS though (and a paid app).

i can't personally recommend it, as i just found it, but 'mindful notifier' on f-droid appears to do what you're looking for.

Maybe you could try Pomodoro? It splits up your time into 25 min chunks, and then you take a break and decide what to do next.

https://todoist.com/productivity-methods/pomodoro-technique

You can setup a countdown timer for 30 mins and restart it every time.

Any app that you can setup Macros with. I use Macrodroid on Playstore.

It seems Tasks.org let's you set reminders on tasks that can repeat every minute (if you go to the custom option). Maybe have a play with that? It's on F-droid.

My comment won't be anything helpful, there are some propositions already.
I just want to give my thought and maybe rant a little, because my Linux nerd mind is screaming to me how this could be done on Linux:

In crontab:

*/30 7-16 * * 1-5 notify-send "Text"

Sending a notification every 30 minutes from monday to sunday from 7am to 4pm with one line of code not needing to create new app.

If the others suggested aren’t quite right for you, you might try looking for an interval timer app. These are generally used for fitness, but it seems to me that type of setup might do exactly what you want if you just set up a “workout” that has a single 30 min interval and repeats.

I feel you. I guess what you need is a chime.

I used an hourly chimer app back when I was studying.

https://play.google.com/store/apps/details?id=com.caynax.hourlychime This is what I could find. Hope this helps.

Can't recall an app like that but I'm willing to bet you can get a digital watch to do that

I like Galarm, it's an alarm app that lets you set any interval you want to repeat, and you can set it to only occur during certain times. I have an alarm that goes off every two hours from 8:30am-8:30pm, for example.

Cuckoo Hourly Chime - A Clock App with Customizable Sounds and Speaking Time

Cuckoo Hourly Chime is an Android application developed by Dev Technosoft that functions as a clock app with customizable sounds and speaking time. The app is categorized under Lifestyle and is available for free.

This clock app offers a variety of features such as more than 10 inbuilt sounds that play every half and full hour, including the option to speak time with a custom title. Users can also choose the hours-only option, wake the screen to stop the chime, and stop the app from the notification bar.

Clock app set many alarms

I use Due on iOS for repeating timers/reminders where I need it to be persistent and annoying because the task is important. Like paying rent, or physical therapy “homework” I kept forgetting. The persistence might be good if you’re worried you’ll just dismiss a normal alarm or forget to start the next timer.

It's not on F-Droid, but I use BlipBlip for this exact thing. It's an old app sadly, but still works on Android 14. There's a ton of customization options which you might find useful.

There’s an app called Interval Timer on iOS.

I’ll leave figuring out what it does as an exercise for the reader

OpenHIIT is a workout timer I've used before. It can handle a simple auto repeating timer.

People using the Pomodoro technique use apps like that. That's usually 25 minutes, 5 minute break, repeated 4 times, then a 30 minute break. This is apparently a popular Android one but there are others for Windows, Chrome, MacOs, I assume Linux and more for Android as well.

I used to have an iPhone app that did this. I kept my phone in my pocket at work and every 30 minutes it would speak the time aloud. You could also configure it to sound a discreet beep instead. I don't remember the name of the app but just want to say this is a really handy tool to have and now your post makes me want to find one for Android.

Reminds me of the character White Rose from Mr. Robot. Here's the introduction scene.

I think I found the one, some app I tried is developed like 7 years ago then I found this which last updated in Feb 2023

here's the link: https://f-droid.org/packages/com.github.axet.hourlyreminder/