Netumo

Pros: The free plan and the affordable prices make the product stand out. Would definitely recommend for small businesses or students who are new to web programming.
Unlimited notifications on apps such as Slack and Telegram helped me to track my website.
Found SSL expiry very useful.
Easy to use with new UI.

Cons: I was quite happy with everything. Never had any issues with Netumo.

Overall: With Netumo, I'm guaranteed to know if my website is down or if there are any performance issues. The prices are much less than other monitoring services and the features given in every plan are very useful. The new UI helped me a lot to integrate with Netumo and to understand how to make use of all the functionality.

Pros: Netumo is has been one of my most reliable tools. The interface is straightforward. The notifications are clear and consistent. Overall design is great.

Cons: None that I've encountered. It delivers what it promises.

Overall: I have been using Netumo for awhile and it has been a pleasure. The notifications are consistent and the service has been more reliable than other similar services that I was using simultaneously. This is a very simple, clean tool.

Pros: Affordable
Easy to setup
Good respond time
SMS and Slack is very helpful
Quick on catching SSL, timeout and other issue with domain

Cons: My agency is quite happy with service, we have not tried any other similar services.

Overall: Very reliable service and must have if you are agency owner looking over bunch of domains. You always need to be on top of all of your domains, and if there is an issue with domain it better to for us to tell client issue and solution , rather then Client asking us why there is an issue with the domain. This is where Netumo comes in play. It keep eye on all of our domains.

Pros: Prompt notification when website is down or encountered a timeout or Tracked SSL Certificate -- Not Found.
Very easy to setup.
Very cheap.

Cons: None. I could not find any negative, price is great as well and free for one single site.

Overall: It works as intended; I have one website I have hosted with not so great hosting company. I have got notification from Netumo I believe every time it's down or SSL not found or encountered a timeout and also when site up and running . I highly recommend this service.

Pros: It's very easy to deploy and implement on any website. It gives SMS and email alert about any performance issues. Realtime alerts and analytics about website up and downtimes.

Cons: Overall it's an outstanding website monitoring tool.

Overall: It's a powerful reminder and monitor tool for the website. Overall I use Netumo on my business website to get alert on SSL and domain expiry. It also provides me health reports and downtime monitoring. It's a very cost-effective tool.