In task https://www.google-melange.com/gci/task/view/google/gci2014/5822912749633536 we created an Oscilloscope using the gstreamer waveform plugin. The problem is two-fold: (1) the plugin doesn't seem to work on some systems; and (2) waveform is pretty specific in its rendering. In this task, can we access the raw microphone data and plot it with Cairo? This would give us more flexibility in the ultimate activity we'd like to create.