I know there are two companies, IK Multimedia and Apogee, that make audio inputs for the iPad. I have both an iRig and an Apogee Jam, and they work great (they're meant for using an electric guitar with Garage Band). Both companies also make audio and mixer inputs for iOS devices. Maybe you could run the audio output from your keyer into an iRig, for example, then from that into the iPad. Might be worth a try?
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