Prefix will help troubleshoot what your code is doing by inspecting key methods, database queries, web service calls, and logging statements.
Prefix is designed for developers to use everyday as they write & test their own code. Prefix answers the question of “What just happened” in my code.
Free to use with a few limitation (shows 1000 latest requests etc.)
Source: What is Stackify Prefix?
Getting started videos:
http://www.dotnetswede.com/prefix-is-out-heres-a-list-of-resources-for-getting-started/