Web app allows you to freely monitor one website for downtimes and to get promptly notified if it does, 100% free.
Key features for fully free version include:
Free version for one website.
Pro version pricing: https://www.webgazer.io/#pricing
My comment: Handy web app to keep an eye on your website downtimes. Particularly useful if you have just published a new website or have moved to a new hosting provider or if you have a website which must be up at all times with as minimum downtimes as possible.
Try it out now: https://www.webgazer.io/