I've been tinkering with this for a while...the older IC-756 doesn't accept all commands via CAT, so I had to come up with a couple of work-arounds, but it works very good now.
I'm using Ham Radio Deluxe for the radio interface software, a generic Icom Programming cable for the CAT interface, the WD7F Keying Utility to trigger the transmitter keying when in phone from a different com port (the 756 doesn't accept TX commands via CAT and must be "hard keyed), the Buxcomm Rascal for the computer/rig audio interface, LogMeIn to connect to the rig remotely, and Skype for the remote audio transport. When operating digital mods remotely, I use DM-780 (built into HRD).
I've posted info, screen shots, an operating tips on my website for those interested. Go to www.WB4IUY.net
, tab over the [WB4IUY] link in the tool bar, and select "Remote Operation".