I don't know about the Iphone apps, but the Android has no problems with refresh rates at all. My Torque Pro pulls in 20-30 PID\S on BT and 40-50 PID\S on USB. As a matter of fact, after talking with Ian Haskins (Torque Pro developer), our cars are the limiting factor in these speeds. The OBD adapters (quality ones) can pull in upwards of 200+ PID\s, but these older cars don't read the sensors that fast. PID\s is basically a sensor read per second. So it'd be checking your knock retard 20+ times per second.
