A quick question tho...The 5D MK II and MK III cannot do this. The feature is being added to the 1D X. You can do it with a Nikon D800.
It works by using the HDMI output, but the output is at reduced resolution in all but the 1D X. This makes direct recording undesirable.
That's incorrect, uncompressed HDMI output will be added to 5D Mark III in April, no plans for 1D X and other cameras yet.
So, after April, 1D C and 5D Mark III are the only two cameras in the Canon DSLR line that are capable of utilising external recorders.
The OP originally asked about recording straight to a laptop, will this be possible with the firmware update to the 5D3, or will it have to be some sort of dedicated external recorder?
yes you'll need a dedicated external recorder like the ninja for this.
as far as i know laptop hdmi ports are hdmi-out only