The Padcaster Audio/Microphone Y Splitter
Padcaster's dual microphone/headphone cable is a simple, professional way to connect your microphone to the iPad. One end is a MALE TRRS (Tip, Ring, Ring, Sleeve) and connects to the iPad's headphone/mic port. The other end splits into a 3.5mm (mini) stereo heaphone jack and a 3.5mm (mini) microphone input so you can record and monitor your sound at the same time.
3.5mm headphone jack
3.5mm microphone input