Your D700's internal flash can be set to commander mode and your SB800 can be put into Remote. You now have a wireless remote iTTL flash system. Only problem is its IR so the SB800 has to be line of sight with the pop up flash to work. If you want a radio solution the Yongnuo and Cactus V5s radio triggers will give you manual triggers for $60. If you want to maintain iTTL you will need to jump to the $340 Phottix Odins.Radio Poppers and Pocket Wizzards are much more expensive.