When you say FM demod you are referring to demodulating and playing the resulting audio waveform? The Spike software has an audio player in the utilities file menu. We are also compatible with an SDR application called HDSDR which has much more extensive audio playing capabilities. You can find the files and setup guide for HDSDR compatibility at this link. https://solutionspagedemo.kinsta.cloud/sigdownloads/Other/HDSDR-SignalHound.zip
If you are referring to frequency vs. time plot or data, you can use our zero span mode for short captures, or our API for continuous I/Q data, which you can FM demodulate using the atan2 function.