Earlier quoted context omitted.
Same here. I need a phone call to pay any attention. I use UptimeRobot and their RSS feed to pipe into a Zapier Zap which uses Twilio to call me and read me the site that is down in a British voice haha. Easy to setup, works and really cost effective!
Too many weak points of failure on that setup for an alerting system.
But I agree for e-commerce or mission critical applications - you need redundancy and it's worth ponying up the extra money for an advanced system.