Use flutter_background_services plugin. You can start a foreground service which will keep running even if the app is terminated.
Here, you can set the interval as low as 1 second.

It is using STICKY service, which basically means, it will restart the service if terminated by the OS.

I want to implement the feature (Example images were attached below) in the flutter application. I want that if I started a service, then it will not be killable till the service end. It will show a notification like this that the application service is still active.
I want a service like this, the application continuously uploads the location of the user to my server in the background continuously.
I tried the plugin work_manager. But this plugin runs the service every 15 minutes (15 minutes is the minimum time we can set).

Example of my requirements:

1. Here in my android task there is no application running.

2. But still, this application is running because the service was enabled.