Heartbeat Monitoring for ESP32, Scripts and Humans Using Home Assistant Webhooks

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1

Hi everyone,

I wanted a simple way to trigger Home Assistant automations when something stops reporting.

Not when a sensor changes state.

Not when a webhook arrives.

But when an expected heartbeat disappears.

Some examples:

  • An ESP32 stops sending data.
  • A remote script stops running.
  • A Raspberry Pi goes offline.
  • A daily operational check is forgotten.
  • A person fails to check in for a predefined period.

I couldn't find a solution that worked the same way for both devices and people, so I built a small service called Dead Man's Hand.

The concept is straightforward:

  1. Create a timer.
  2. Periodically renew it through the web UI or REST API.
  3. If the timer expires, execute actions.

One of those actions can be a Home Assistant webhook.

This allows workflows such as:

ESP32 → periodic heartbeat → timer renewed

ESP32 offline → timer expires → Home Assistant webhook triggered → automation runs

The same mechanism can also be used for:

  • monitoring external services
  • monitoring remote locations
  • backup verification reminders
  • maintenance reminders
  • family safety check-ins
  • digital inheritance workflows

Anything capable of making an HTTP request can renew a timer, including:

  • ESPHome
  • ESP32
  • Raspberry Pi
  • Shell scripts
  • Cron jobs
  • CI/CD pipelines
  • External services

I would love feedback from the Home Assistant community.

How are you currently handling heartbeat monitoring and "if something stops reporting" automations?

Project:

https://deadmanshand.pp.ua

2

Maybe a stupid question, what is the registration for?

3

A watchdog timer?

There is no state change reported for missing state changes in HomeAssistant (obvious logic).

This could be a desired option, (especially for devices that have a protocol and name starting with the letter "Z"), but would be a change request, and probably involve configuring polling and timing loops.

4

sorry, WHAT? :slight_smile:

5

Hi!
Not bad. Generally speaking, registration is needed so that the system can distinguish one user from another and preserve state between sessions.

6

The renewal is the feature :slightly_smiling_face: It prevents "set and forget" reminders. You can renew it manually in the UI or automatically from Home Assistant via API.

7

Similar idea, but it's intentionally focused on people and their responsibility, not just the heartbeat of devices. A watchdog timer checks to see if the system is alive; a dead man's switch checks to see if anyone is still actively asserting responsibility.

8

The service has moved to a new address: https://dmh.syntrope.app/