Was it up?-service is now offline.
wasitup.com
wasitup.com
As I've mentioned elsewhere: if time permits I'll have a go at re-launching with a new back-end and subscriptions (hopefully Stripe will be available in Europe soon) for the most heavy users.
Why don't you do something like reach out to hacker news users. I'm sure there's some aspiring biz dev types with a little bit of capital (sounds like you only need a couple hundred dollars a month to keep it operating) to invest some time and money into your business. Then you have a little time to pivot into a money-making version of your site... fremium of whatever model makes sense.
But right now you have one of the toughest things to get... a bunch of users. (myself included) Don't squander them!
As a casual user, I would have paid money if you had an option to watch 1-5 servers.
Good luck with a relaunch, if that's what you decide to do. (And good luck with whatever else you decide to work on)
Not that hard to do if you have access to multiple servers to monitor each other, it's a good coding exercise.
Just use curl and grab all the curl_getinfo results, including the dns resolve time to the firstbyte time to the page size and page transfer speed/time.
Log it, graph it, and if you get a bad result, email yourself an alert.
Don't forget to exclude the polling server from your stats!
Anyway -- signed up for pingdom.com and it looks solid enough.
Disclosure: I am the founder (on the other hand, this means I can assure you that the free plan is really free and we have no plans to change that).
We've been monitoring hundreds of thousands of sites for years, and our pricing is low.