In theory it's as simple as reading your executable code, then addressing the instruction pointer to the beginning of your binary resource and off it goes...
I just have to point out this isn't correct. You can't point the instruction pointer to some "binary resource", whatever that means.
Processors like the Arduino use the Harvard architecture.http://en.wikipedia.org/wiki/Harvard_architecture
You cannot execute instructions from RAM. Wanting to won't change that basic fact. Nor will moving the instruction pointer.
I was thinking windows at the time, i've actually downloaded an entire exe into memory and then executed it!
but obviously there are restrictions i have no clue about... In my head I was thinking he meant something like a library (eg send over serial 50 bytes of executable instructions) then push pop whatever onto the stack and mess with the instruction pointer ..
But, if you have access to the instruction pointer why not be able to store that into ram and execute it?...