Skylight is a smart profiler for Ruby and Rails applications. It turns performance data into actionable insights, so you spend less time diagnosing and more time improving.
Monitive is an uptime monitoring service, where users sign up and input their website address, which we check every minute, from a random location around the world, and instantly notify them when their site is down.
Kamon is a monitoring toolkit for applications running on the JVM. It gives you Metrics, Tracing and Context Propagation APIs without locking you to any specific vendor.