I found this thread by looking at what TCP connections Safari was making while connected to the MobileSafari inspector, seeing that it was connected to a process called webinspectord and Googling that:
# pgrep -lf /Applications/Safari.app
33170 /Applications/Safari.app/Contents/MacOS/Safari -psn_0_21144617
# lsof -p 33170 | grep TCP
Safari 33170 ryan 16u IPv6 0x799d5f43b472a241 0t0 TCP localhost:54892->localhost:27753 (ESTABLISHED)
# lsof -i :27753
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
launchd 371 ryan 42u IPv6 0x799d5f43b472aa01 0t0 TCP localhost:27753 (LISTEN)
Safari 33170 ryan 16u IPv6 0x799d5f43b472a241 0t0 TCP localhost:54892->localhost:27753 (ESTABLISHED)
webinspec 33182 ryan 6u IPv6 0x799d5f43b472aa01 0t0 TCP localhost:27753 (LISTEN)
webinspec 33182 ryan 7u IPv6 0x799d5f43b181a621 0t0 TCP localhost:27753->localhost:54892 (ESTABLISHED)
# ps p 33182
PID TT STAT TIME COMMAND
33182 ?? S 0:00.28 /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator6.1.sdk/usr/libexec/webinspectord