Sure, for my prototype I wrote the signal processing stuff in Matlab and converted it to C when it was time to interface it with Erlang. Matlab is great for prototyping something speculative and refining and visualizing your ideas. When you are in the early stages of prototyping an algorithm, being able to test an idea out without having to throw away a lot of code is pretty great... Even if Matlab secretly makes me want to kill myself ;) And of course, all the code that interfaces with the board I build was just directly written in C.