I tried to use this and it showed me an apache2 landing page instead of my app website, which led me to realise my app site had been down for at least a day because apache had actually crashed due to nginx using port 80 (I don't even use nginx so not sure what the heck happened)

Anyway, not the success story I'd hoped to post here, but it definitely solved at least one problem I didn't know I had.

I'm now going to add uptime monitoring