Dennis O’Clair from MarkerTek.com was nice enough to send me a cable to review to defeat or disable the AGC on the Canon DSLR like the 7D and T2i/550D.
It appears to be well made and works just fine as you can see in the video.
I think it is a little pricey at $26.95, but it is a very special cable that they mostly like will not make a ton of them. I made mine for a lot cheaper, but if you do not know how to solder this can be a big help.
See my site link above to find out where you can get it.