If you want a simple way to keep an eye on your website's uptime and downtime right in your Slack channel, Simple Uptime is a great option. The service is tightly integrated with Slack so your team can keep tabs on website, API and server availability right in your channel. It monitors continuously, lets you set up alerts, and requires no extra tools or services. And the best part? It's free, so it's a good option for smaller teams that want to keep an eye on their website's status without a lot of hassle.
Another option is Rupert, a no-code monitoring and alerting service geared for product-led growth teams. It's geared for monitoring user-level metrics and events, but it also offers a Slack integration so you can get alerts in your channel. It's good for teams that want to prevent churn, get new users up and running and accelerate growth. It offers a free plan with limited alerts and several paid tiers for larger teams.