Amon - Python-powered server monitoring, logging, and error reporting with JSON API

Amon from Martin Rusev is a simple yet flexible way to add server monitoring, logging, and error tracking to your web stack. Amon consists of three parts: a collector daemon, a Python web app, and JSON API.

• Collector daemon - Amon’s server and process monitoring is a thin wrapper on top of Unix tools to record metrics and store them in the MongoDB backend.
• API - Shipping with language bindings for Python, Ruby, and JavaScript, Amon’s JSON API makes it easy to record your own application events.
• Web interface - The web app provides a friendly user interface for viewing logs and visualizing data in charts.

The Amon documentation site is a great place to get started with installation and usage.