A constant reminder to sit up straight...

crontab

*/5 * * * * /<path-to>/bin/node ./<path-to>/sayPosture.js >/dev/null 2>&1

sayPosture.js

#!/usr/bin/env node
// cspell:ignore Veena

const { exec: execWithCallback } = require("child_process");
const { promisify } = require("util");

const exec = promisify(execWithCallback);

// --- config:

const VOICES = [
  // "Alex", //     en_US    # Most people recognize me by my voice.
  "Daniel", //      en_GB    # Hello, my name is Daniel. I am a British-English voice.
  // "Fred", //     en_US    # I sure like being inside this fancy computer
  "Karen", //       en_AU    # Hello, my name is Karen. I am an Australian-English voice.
  "Moira", //       en_IE    # Hello, my name is Moira. I am an Irish-English voice.
  "Rishi", //       en_IN    # Hello, my name is Rishi. I am an Indian-English voice.
  "Samantha", //    en_US    # Hello, my name is Samantha. I am an American-English voice.
  "Tessa", //       en_ZA    # Hello, my name is Tessa. I am a South African-English voice.
  "Veena", //       en_IN    # Hello, my name is Veena. I am an Indian-English voice.
  // "Victoria", // en_US    # Isn't it nice to have a computer that will talk to you?
];

const PHRASES = [
  "Are you sitting straight?",
  "Posture!",
  "Slouching again?",
  "Straighten up!",
  "You're slouching again!",
];

// --- helpers:

const getRandom = (arr) => arr[Math.round(Math.random() * (arr.length - 1))];

const isOffZoom = () =>
  new Promise((resolve, reject) => {
    /*
    > lsof -i 4UDP | grep zoom
    zoom.us   30869 philipblyth   65u  IPv4 0xba9851d3ed103735      0t0  UDP syncsketch-mbp.hsd1.ma.comcast.net:53619
    zoom.us   30869 philipblyth   66u  IPv4 0xba9851d3ed103d15      0t0  UDP syncsketch-mbp.hsd1.ma.comcast.net:57360
    zoom.us   30869 philipblyth   67u  IPv4 0xba9851d3ed1013f5      0t0  UDP *:51655
    zoom.us   30869 philipblyth   76u  IPv4 0xba9851d3ed106c15      0t0  UDP *:53042
    zoom.us   30869 philipblyth   78u  IPv4 0xba9851d3ed1080a5      0t0  UDP *:50107

    > lsof -i 4UDP | grep zoom | wc -l
           5
    */
    // NOTE: needs to be full /usr/sbin path to work inside `crontab` :(
    exec("/usr/sbin/lsof -i 4UDP | grep zoom | wc -l")
      .then(({ stdout }) => {
        stdout.trim() === "0" ? resolve() : reject(Error("Zoom is active!\n"));
      })
      .catch((err) => {
        reject(err);
      });
  });

// --- run!

isOffZoom()
  .then(async () => {
    const voice = getRandom(VOICES);
    const phrase = getRandom(PHRASES);

    // log:
    process.stdout.write(`${voice}: "${phrase}"\n`);
    // say:
    await exec(`say -v ${voice} "${phrase}"`);
  })
  .catch((err) => {
    process.stderr.write(err.message);
    process.stdout.write("Silencing.\n");
  })
  .finally(() => {
    process.stdout.write("Done! 👍\n");
  });

Sadly, the env available to crontab is very limited, so you can't simply rely on the #!/usr/bin/env node line, but instead need the full path to node, even though cron runs as the current user...