I just saw this: http://hackaday.com/2014/07/22/talking-beagleboard-with-jason-kridner/
It's a 14-channel 100Msps logic analyzer using the BeagleBone Black and no additional hardware - it makes use of the on-chip dual programmable real-time units (PRUs).
Apparently it has been used to capture sustained >100MByte sized data streams : ) And also for I2S audio data capture : ) It would be ideal for digital audio testing!
Highly impressive stuff.
The BBB has evolved into the universal test tool that we always suspected it could become.
Multifunction instrument based on BeagleBone Black