Since entering paternity leave, I have had little time to come up with something new to post here. However, one colleague was so kind as to send me his Windows version of the live fourier transform program discussed before. His runs on his Lenovo laptop (but may be more widely applicable) and uses the Windows built-in Matlab webcam code. Framerates are markedly better than my OS X code, but memory requirements are significant and reinitialisation of the camera every few seconds generates a flash.
The code is available here, with many thanks to Jakob R. Eltzholtz for making his code available. If you have suggested improvements or changes, please do not hesitate to contact Jakob and/or me.