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Qloudstat - Analytics & monitoring for access logs in Amazon S3, Amazon CloudFront, Google Cloud Storage and Rackspace CloudFiles (Akamai CDN)
S3Log - Delivering hourly S3 log file analysis.
amon - Self-hosted server and app monitoring tool
Checkmk - Checkmk - the software for effective IT monitoring
LogDNA - Cloud log management system.
Trafikito - Monitor CPU, RAM... or output of any command and make API call on event, default is email messages.