Followup on the iPhone as a wired remote control for K2:
Thanks to the redpark.com cable, it's working - got a prototype iPhone app
doing reads/writes directly with no need for Wi-Fi, Bluetooth or other
devices inbetween (well there is an embedded controller inside the cable,
but the cable still just looks like a cable).
Since the K2's AUX I/O pinout isn't the same as the RS-232 standard (NEVER
attach a 'full' RS-232 cable directly to the K2!) a second cable is needed
between the K2 and the redpark cable. In my case I simply wired pin 2 to 2,
pin 3 to 3, pin 5 to 5 (signal ground). Also, on the K2 end only, attached
the bare wire to pin 1 (chassis ground), and on the end that mates to the
redpark cable, wired pin 7 to 8 (RTS/CTS loopback, see p. 13 of Elecraft
KIO2 manual, Rev. C).