Perhaps you are not aware of it, but there are plenty of places where you can get a totally free website monitoring service for your website.
Of course you can google the “free website monitoring” keyword and check site by site, but… don’t. We did it for you.

In the first place we have excluded all the “free trial” options. They are free, but only for a limited time – usually 7 to 30 days. Afterwards you need to pay or resign.
Then we have visited tens of websites offering a real free and time-unlimited service of website availability monitoring. We have chosen twelve of them – that seemed working and reliable. There are some slightly differences among them, but the only important feature that lets compare them is the frequency of the tests.
While commercial monitoring services offer intervals down to 1 minute, free ones check your website every 5-60 minutes.
(60 minute interval has no sense at all. Imagine server administrator that wouldn’t notice and fix the failure in 1 hour…).

OK, here is the list with links. The choice is – as always – yours.

If you need a professional 1-minute monitoring service, check the “15 website monitoring services compared” article.