I'm running into incomplete documentation or irrelevant situations in trying to understand this, so I need help in straightening my definition of this environment.
I have an instance of Nagios, an instance of Splunk, and a working Livestatus that provides a socket for which data from Nagios can be obtained. I understand that Livestatus can pull information from Nagios such as echo 'GET hosts'|unixcat /path/to/livestatus/live/socket. Another additional way of using Livestatus is creating files that contain custom queries which can have an organization of data as well as a filtering of data in order to provide items of relevance and importance and using unixcat < queryName path/to/livestatus/live/socket.
However, based on what I've seen Splunk do, it's simply pulling all the information in from Nagios, disregarding the Livestatus Queries. This begs the question of how do I get Splunk to receive filtered data from Nagios so as an example, receive data that a logging service is down and not within scheduled down time? Once that data has been filtered, where on Splunk am I able to view the data of that query?
I don't know of any out of the box integrations with Livestatus so you'd be on your own writing a scripted or modular input to pull data in that way. I wouldn't re-invent the wheel here. Splunk as written the Splunk Add-On for Nagios Core. It uses NDOUtils to pull data from Nagios and index in Splunk. You can view all the different sourcetypes that the app pulls in here. if you're interested in scheduled downtime look at the sourcetype nagios:scheduleddowntime
The requirement for NDOUtils is a little more heavy-weight than Livestatus but it will save you the trouble of having to build your own integration. A small price to pay in my opinion.
have NDOUtils installed on your Nagios instance
have an account with read privileges on the MySQL database of NDOUtils
have Splunk DB Connect v2 installed on the heavy forwarders responsible for data collection.