Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.
Checkout Page - Sell on your site with customizable checkouts. Tailor-made one page checkouts to sell digital products & services without an ecommerce store.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Stripe - Online payment processing for internet businesses. Stripe is a suite of payment APIs that powers commerce for online businesses of all sizes. Use Stripe’s payment platform to accept and process payments online for easy-to-use commerce solutions.
Better Uptime - We call you when your website goes down
Stripe Elements - Beautiful, smart checkout flows 💳💸