airbrake-ruby (rubygems): Airbrake Ruby is a plain Ruby notifier for Airbrake (https://airbrake.io), the leading exception reporting service. Airbrake Ruby provides minimalist API that enables the ability to send any Ruby exception to the Airbrake dashboard. The library is extremely lightweight and it perfectly suits plain Ruby applications. For apps that are built with Rails, Sinatra or any other Rack-compliant web framework we offer the airbrake gem (https://github.com/airbrake/airbrake). It has additional features such as reporting of any unhandled exceptions automatically, integrations with Resque, Sidekiq, Delayed Job and many more. 
Keywords: airbrake|apm|crash-reporting|error-monitoring|performance-monitoring|ruby