There was a Nokia-9600S reciever that had a built-in SCSI-II port, so you was capable transfer your sattelite data flow to a computer.
They are out of production, people like RIAA made Nokia stop making them. If you are lucky you can still get a used one for a decent price, and finding "special" firmware must not be a problem too at
http://www.no-access.deThere are also solutions like SkyStar PCI reciever boards or Dreambox recievers that have a 100Mbit Ethernet built in.
I am not a specialist in this field, only helped to "compress" some non-copyrighted material to DivX.
The audio-stream from most of sat-radio stations is already in MP3, so you only have to capture it. Bitrates are quite high, 192-256 is a common thing, but some stations transmit in 384.