Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.
Haark - Tracks your sites and notifies you if they're down
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Rollie - Know where your money goes. Spending tracker for iPhone.
Better Uptime - We call you when your website goes down
CostTeam - Identify online subscriptions and other recurring expenses.