Cloudlytics - Analyze Your Amazon S3 & CloudFront Logs.
amon - Self-hosted server and app monitoring tool
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.
Checkmk - Checkmk - the software for effective IT monitoring
Trafikito - Monitor CPU, RAM... or output of any command and make API call on event, default is email messages.
OverOps - Know why Java code fails in production. Get the full Java source code and variable state for every error. Reproduce and Fix critical issues in seconds.