I get what you're saying, but I think you're being overly skeptical. If you've already got a system for monitoring tasks in place, there's no reason you couldn't run both. And if you don't have a system in place, then if it fails you'll be no worse off than having never signed up.

I think most SLAs for these types of services are mostly pointless anyway. If something important to your business goes down, are you really going to be worried about whether or not you have to pay the $19?