Checkmk - Checkmk - the software for effective IT monitoring
S3stat - S3stat is a service that takes the detailed server access logs provided by Amazon's CloudFront and Simple Storage Service (S3), and translates them into human readable statistics, reports and graphs.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Qloudstat - Analytics & monitoring for access logs in Amazon S3, Amazon CloudFront, Google Cloud Storage and Rackspace CloudFiles (Akamai CDN)
Trafikito - Monitor CPU, RAM... or output of any command and make API call on event, default is email messages.
Bugfender - Cloud logging for your apps, not only crashes matter