Now's a good time to decide what you want to do after you finish your course.
Then you can pick a topic that compliments it (and would look useful on your CV).

I got my first programming contract on the back of my MSc project (serial port control of laboratory equipment --  it was more than a decade ago Smiley ).

VOIP sounds like a good choice, make sure your backup plan is also relevant to what you want to do next.