I triple-stacked as soon as I could, and I'm very glad I did.

Monspark is a superb piece of kit!
I've tried a few other monitoring tools, and refunded due to limited feature sets, iffy roadmaps and slow customer support.

Monspark has more features/monitor-types than any other monitoring tool I've found, and they're still pumping more out!
My favourites are the sitemap monitor, and the screenshot monitor, which checks your site for visual changes. This is perfect for me, as a web designer, because I can keep track of any mistakes my clients make post-handover.

Customer service is epic, too. Super friendly live chat, even on the weekends.

This is a platform that is going to go very, very far.
In a year or so, I reckon you'll kick yourself for not buying in now.