In general it was built for math and signal processing (broad field). Within those fields, more specifically it was designed initially for real time signal processing (image analysis, communication, decryption). Turns out that makes it a pretty good fit for other things as well (like neural nets..). Here is the publication list showing some of the apps. (for later, server is flooded now): http://parallella.org/publications
In the paper they are suggesting deep learning, self-driving cars, autonomous drones and cognitive radio.
What is cognitive radio?
Maybe that's what they call speech recognition?
Dynamically switching carrier frequencies to make better use of the spectrum. It is somewhat related to software-defined radio, in that SDR's are typically used to prototype cognitive radio.
It hasn't really got mindshare though in the sense players like Qualcomm have all but ignored it and would rather work on proprietary comms schemes.
Dynamic spectrum management, changing channels based on current usage and other factors.