It is a service to update different search engines that your blog has updated.
Service is looking for the latest entry into the submitted feed, then send an XML-RPC signal to ping servers and finally returns feed's content.
Used ping servers:
It uses Universal Feed Parser so it can handle RSS 0.90, Netscape RSS 0.91, Userland RSS 0.91, RSS 0.92, RSS 0.93, RSS 0.94, RSS 1.0, RSS 2.0, Atom 0.3, Atom 1.0, CDF feeds and several popular extension modules (for more information see Universal Feed Parser documentation).
Usage: http://bloggersayshey.appspot.com/retransmitter?feed=FEED_URL where FEED_URL is an http or https URL of feed.
Author: Andrey Khoronko (blog).