Your sensors, on WhatsApp.

Greenhouse too cold, water tank full, garage door opened at 3am — the board POSTs, your phone buzzes. One HTTPS request to POST /v1/notify from whatever the thing runs: Arduino C++ on an ESP32, MicroPython, or a cron line on a Raspberry Pi. No app to install on the phone, no linked device, no phone-number pairing — it's the official Meta Cloud API underneath.

WiFiClientSecure + HTTPClient, both in the ESP32 Arduino core — no extra libraries. Call notify() from wherever your sketch decides something's worth a buzz. Get the key by sending join on WhatsApp (details at the bottom).

#include <WiFi.h>
#include <WiFiClientSecure.h>
#include <HTTPClient.h>

#define PINGWA_KEY "pw_your_key_here"

// call after WiFi.begin(...) has connected
void notify(const String &text) {
  WiFiClientSecure client;
  // Trade-off, stated plainly: setInsecure() still encrypts the
  // connection but skips certificate validation — fine for a
  // greenhouse ping, wrong for anything secret. The proper fix is
  // client.setCACert(root_ca) with the root CA PEM in your sketch.
  client.setInsecure();

  HTTPClient http;
  http.begin(client, "https://pingwa.dev/v1/notify");
  http.addHeader("Authorization", "Bearer " PINGWA_KEY);
  http.addHeader("Content-Type", "application/json");
  int code = http.POST("{\"text\": \"🌡️ greenhouse 4°C\"}");
  http.end();  // code == 200 → queued; negative → connection/TLS error
}

urequests ships with standard MicroPython builds for the ESP32 — import urequests just works, no mip install needed. The json= argument handles the body and the Content-Type header for you.

import urequests

def notify(text):
    r = urequests.post(
        "https://pingwa.dev/v1/notify",
        json={"text": text},
        headers={"Authorization": "Bearer pw_your_key_here"},
    )
    r.close()

notify("💧 tank full — pump stopped")

If it runs cron and curl, it can tap you. The || true matters: a ping that fails (WiFi blip, our outage) must never break the job it's reporting on.

0 22 * * * /home/pi/backup.sh && curl -sf -X POST https://pingwa.dev/v1/notify -H "Authorization: Bearer $PINGWA_KEY" -H "Content-Type: application/json" -d '{"text": "🍓 pi backup done"}' || true

For threshold sensors, the trap is alert-per-reading: the tank crosses 90% and every 5-minute poll fires another message. The Idempotency-Key header fixes it server-side — the same key with the same body is honored for 24 hours, so replays are absorbed and nothing is re-sent. Key it on the state plus the day and you get one alert per state-change per day, straight from a dumb polling loop:

#!/bin/sh
level=$(cat /var/lib/tank/level)   # your sensor read here
if [ "$level" -gt 90 ]; then
  curl -sf -X POST https://pingwa.dev/v1/notify \
    -H "Authorization: Bearer $PINGWA_KEY" \
    -H "Content-Type: application/json" \
    -H "Idempotency-Key: tank-high-$(date +%F)" \
    -d '{"text": "💧 tank above 90% — check the pump"}' || true
fi

One rule to respect: keep the body constant for a given key. A different body under the same key is rejected with a 409 and nothing is sent — so don't interpolate the live reading into the alert text, or the second poll's "91%" vs the first's "90.4%" turns your dedupe into a silent drop.

Scan the code and get instant access. It opens WhatsApp with “join” ready to send, and your API key comes straight back.

The snippets above are the honest shape of the integration, not lab-verified on every board revision — pin versions and test on your own hardware before trusting a greenhouse to it.