The scout gem reports metrics to Pingdom Server Monitor (server.pingdom.com), an easy-to-use hosted server monitoring service.

Dump the Twitter streaming API to a CSV or JSON file and then filter, handle retweets, apply sentiment analysis, and more.

Twitter-to-Jabber gateway.

Strumento di monitoraggio di Euro Servizi S.r.l.

Like Rack::File, but it serves the last lines of a file

This gem is deprecated - see rack-tail

Scout is a full server monitoring solution. You can install standard plugins to get started with basic monitoring right away, or build your own plugins to address your specific needs. Scout can be tied into any monitoring strategy, providing you data collection, trend analysis, email notifications and more.