SignalScope necessarily disables audio from any other app that may be running on the iPhone, so SignalSuite and SignalScope cannot run at the same time.
You may be interested to know that the signal generator tool, which is available for purchase within SignalScope, automatically synchronizes swept sine and periodic pseudorandom noise sequences with the length of the FFT employed by the FFT analyzer. This means that clean frequency response magnitude measurements can be made very easily with little or no averaging (see the SignalScope Pro demo video
for an example of this with an external equalizer).
Also, the IOScope app is a dual-channel analyzer, which is designed for frequency response magnitude and phase measurements, as well as impulse response and correlation measurements.