A couple of days ago some random surfing led me to similar sites, and I started writing a post on my blog about the uptime monitoring services. I came across several 'lists' from posts by KeyCDN, and other sites. Posting some of them here.

The below list includes Free, Freemium and paid services. With time, I will update and classify these services into these three categories, similar to the way I had done in my blog post on Webpage Builders.
As always,

• Suggestions to the list welcome and appreciated.
• If you have used any of the services in the list other than the "LE* favourites", please mention your feedback about them in the comments.

The Big List of Website Monitoring Services

(Posting in random order)

*Types: Free, Freemium, Premium.
Note - 1. for sake of simplicity, paid-only plans are tagged as premium. This category may be updated at a later time
2. I am not a fan of classifying services based on price alone. But in the LE world, that could be used as a filter or starting point.

p.s: Link to my blog post I was referring to

Edit:
a. You will have to provide credit card information / pay $ 0 via PayPal
b. click to disable the 'auto renewal' option.