The Ruby Simple Exception Notification (a.k.a Rusen) gem provides a simple way for logging and sending errors in any ruby application.
Angus is a REST-like API framework which fits perfectly with Ruby. It is based on rack, so it can be used to complement an existing app or as standalone service to easily develop RESTful APIs.
Ruy defines an easy-to-learn language which allows users to declare context-driven conditional expressions.
Sidekiq-scheduler is an extension to Sidekiq that adds support for running scheduled. Scheduled jobs are like cron jobs, recurring on a regular basis.