Apple's variant of ptrace()

Have you ever tried to create a debugger for Mac OS X? It is an adventurous enterprise with lots of unexpected (should I say unforeseeable?) problems. This guy tried and described his adventures in this entertaining post:
http://www.matasano.com/log/1100/what-ive-been-doing-on-my-summer-vacation-or-it-has-to-work-otherwise-gdb-wouldnt/
His post reminded me of all problems we faced with the first version of the IDA debugger for iMac. They also reminded me of even more convoluted puzzles with the iPhone debugger because ptrace() is broken beyond any hope there (one simple rule: use only PT_TRACEME).
Anyway, if anyone wants to repeat our steps, we are giving away the source code of all debugger modules with the new IDA v5.3: iMac and iPhone debugger codes included. They can certainly help you to avoid some headache and frustration!