google-meet-timer.user.js

// ==UserScript==
// @name         Google Meet Timer
// @namespace    https://seanmcp.com
// @version      0.1.1
// @description  Adds a simple, chat-powered timer to your Google Meets
// @author       Sean McPherson
// @match        https://meet.google.com/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=google.com
// @grant        none
// ==/UserScript==

(function() {
    document.querySelectorAll('[data-userscript-gmt]').forEach(n=>n.remove())

    // Styles
    const style = document.createElement('style')
    style.dataset.userscriptGmt = 'styles'
    style.innerText = `

[data-userscript-gmt="toolbar"] {
    background: hsla(0, 0%, 0%, 75%);
    border-radius: 8px;
    color: white;
    display: flex;
    gap: 8px;
    left: 50%;
    padding: 8px;
    position: absolute;
    top: 16px;
    transform: translateX(-50%);
    z-index: 1000;
}

[data-userscript-gmt] span {
    font-size: 15px;
}

[data-userscript-gmt] * {
    border: none;   
    border-radius: 4px;
    padding: 4px 8px;
    font: inherit;
}

[data-userscript-gmt] input {
    background-color: #f1f3f4;
    color: var(--gm-outlinedtextfield-ink-color,#3c4043);
    width: 4ch;
}

[data-userscript-gmt] input[disabled] {
    opacity: 0.5;
}

[data-userscript-gmt] button {
    background-color: var(--gm-body-text-color);
    color: white;
}
`
    document.head.appendChild(style)

    const toolbar = document.createElement('div')
    toolbar.dataset.userscriptGmt = 'toolbar'
    document.body.appendChild(toolbar)

    const input = document.createElement('input')
    input.ariaLabel = 'Minutes'
    input.placeholder = "Minutes"
    input.type = "number"
    input.min = 1
    input.max = 30
    input.value = 5
    toolbar.appendChild(input)

    const set = document.createElement('button')
    set.textContent = "Set timer"
    toolbar.appendChild(set)

    const cancel = document.createElement('button')
    cancel.textContent = "Cancel timer"
    cancel.hidden = true
    toolbar.appendChild(cancel)

    set.onclick = function(e) {
        e.preventDefault();

        try {
            // Check if the chat window is closed
            if (!document.querySelector('[role="heading"][aria-level="1"]')) {
                document.querySelector('[aria-label="Chat with everyone"]').click()
            }

            const textarea = document.querySelector('textarea[aria-label="Send a message to everyone"]')
            const submit = document.querySelector('[role="button"][aria-label="Send a message to everyone"]')

            function sendMessage(text) {
                textarea.click()
                textarea.value = text
                submit.removeAttribute('aria-disabled')
                submit.removeAttribute('disabled')
                submit.click()
            }

            function setTimer(minutes) {
                const readableMinutes = `${minutes} minute${minutes != 1 ? 's' : ''}`

                sendMessage(`⏳ Timer set for ${readableMinutes}`)

                window.googleMeetTimer = setTimeout(()=>{
                    sendMessage(`🔔 Time is up (${readableMinutes})`)
                    cleanUp()
                }
                , minutes * 60 * 1000)

                if (minutes >= 2) {
                    window.googleMeetWarningTimer = setTimeout(()=>{
                        sendMessage(`⌛️ One minute left`)
                    }
                    , (minutes - 1) * 60 * 1000)
                }

                window.addEventListener('keydown', function(event) {
                    if (event.key === 'Backspace' && event.ctrlKey && event.shiftKey) {
                        cancelTimer()
                    }
                })
            }

            setTimer(input.value)

            function cleanUp() {
                clearTimeout(window.googleMeetTimer)
                clearTimeout(window.googleMeetWarningTimer)

                input.removeAttribute('disabled')
                set.removeAttribute('hidden')
                cancel.hidden = true
            }

            function cancelTimer(e) {
                e.preventDefault()
                sendMessage(`🗑 Timer cancelled`)
                cleanUp()
            }

            input.disabled = true
            set.hidden = true
            cancel.removeAttribute('hidden')
            cancel.onclick = cancelTimer
        } catch (error) {
            alert('Uh oh! Something went wrong setting that timer.')
            console.error('Google Meet Timer', error)
        }
    }
}
)()

Hi.
Your script interests me.
But, how do you use it in google meet?

@jlrevel I haven't used this in a while and it is currently broken 😞

If I get around to fixing it I will notify you with the steps to get it working.