Webhooks from Android Apps
I have a setup where I receive various events from online services as webhooks and process them, primarily for live analytics but some for actions too. But I use quite a few Android apps that don't have server components. They are simple apps that store data and events locally. I have to sync manually by exporting. Also, syncing events once a month doesn't make much sense.
But it doesn't take much for Apps to send webhooks to any server. It can be done. I am not sure why the native application developers don't usually think about it. It can make so many offline apps very useful. This is, of course, can be in addition to the export feature or any other application-specific web integration.
Webhooks don't have to be from a traditional server to a web server. Webhooks can come from any software component which can connect to the internet (or intranet) and send HTTP requests. One such example is the "Sleep As Android" App. It's an app that tracks sleep. It can raise multiple events like sleep_tracking_started, time_to_bed_alarm_alert etc. You configure any URL to receive these events and perform certain tasks. For example, time_to_bed_alarm_alert can be hooked to an alert service that sends a popup to my desktop or TV. So I have enough time to close the day. Currently, I have hooked it up to HomeAssistant to take action.
What "Sleep As Android" app has done can be done by many other offline-only Apps. For example, Antennapod podcast player can push events like "started_podcast_epsisode,"completed_podcast_episode" etc. Your running app can push run completed hook, your alarm app can send alarm triggered, your GPS app can send the live location (GPSLogger does it), and your SMS app can send an incoming message. They all can be useful to the user.
Currently, you have to hack your way using Tasker or Macrodroid. But nothing like native app support.