Monibot
Monibot monitors your servers and applications and notifies you if something goes wrong. Monibot monitors the following performance indicators and metrics: CPU/Mem/Disk Usage, Disk/Network IO Activity, Database Size, DB Transaction Latency, Website Uptime, HTTP Response Latency, SSL/TLS Certificates, Cronjob Heartbeats, Number of served requests, HTTP Error Rates, and many more.
Pricing
Their free plan is made for smaller and private projects (monitoring of 2 websites). The paid plans are at 7€ per month for 5 websites and 24 € for 20 websites.
Read more on the pricing page of the service.
Hosting
Monibot is hosted in Germany.