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.
Memory Magic - Memory Magic monitors your Mac's memory usage and transparently performs optimizations aimed at freeing/relocating memory.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Memory Optimizer - Here at Softorino – we craft software that simplifies your life.
Better Uptime - We call you when your website goes down
CleanMem - CleanMem keeps memory use in check on the system without the memory being pushed to the page file.