Pingdom
Swedish uptime monitoring that pings your site from around the world and alerts you before customers do.
Pingdom was founded in 2007 in Sweden by Sam Nurmi and made its name on simple uptime monitoring: the service hits a website at regular intervals from probes around the world and alerts you when the response fails or slows down. Real user monitoring (RUM) and page performance came later.
The model — synthetic monitoring from the outside rather than agents inside the system — complements APM tools like New Relic. SolarWinds acquired Pingdom in 2014 and still runs it as part of its observability suite.