I'm not sure I fully understand this article, not being a tech type, but I'm sure Saul could explain it more. It's software that records RDS signals - the technology that displays a station's I.D. and song info on your radio - and tells you what signals it received, even if you're not there to listen to it in the middle of the night. 

"[The] software commands the radio to tune to each broadcast frequency for a few seconds, scanning from the bottom of the band to the top.

 As it scans, it collects any available RDS Program Identification codes. Once the radio reaches the top of the band, a payload containing the frequency, PI code and the time of reception is sent to RabbitEars.info, tagged with the user’s ID."
 
There's a map here that shows what DXers in various areas were able to receive in almost real time. 

Rather than try to explain what I'm not sure about, I'll direct you to the article below for more details. 

FM Autologging Made Easy