Updown.io

Updown.io is a French website monitoring service built and run by independent developer Adrien Rey-Jarthon. It performs HTTP(S), TCP and ICMP checks at intervals from 15 seconds to one hour and reports downtime, slow responses, bad status codes and SSL issues. Pricing is unusually granular: a pay-as-you-go credit model where one check costs one credit, working out to around 0.60 EUR per month per site at one-minute frequency. New accounts get 100,000 free credits, often enough for a full year of light use. Public status pages are included.