>>> Check out the demo videos at onyx3.com/LatencyMeter
LatencyMeter app measures the real-world Round Trip Latency (RTL) of a given iOS audio system*. It functions by playing short test tones while simultaneously recording (listening for) the tones to return back to the input. This technique requires patching a loopback cable between audio systems input and output.
(* iOS audio system here refers to the combination of an iPhone/iPad paired with particular external audio interface)