I don't think either system will work. The SB-400 was designed to be used On Camera ( attached to the cameras hotshoe) and Can only be set in manual flash mode through the cameras menu.
Both the Cowboy NPT-04 wireless remote trigger system and the Yongnuo RF-602 wireless remote system only support Manual flash mode. Therefore you will need an SB-600, SB-700, or other model Speedlight that has Manual flash mode in order to use either system.
You can use an SC-28 or SC-29 TTL extension cord to get your SB-400 Off Camera. This way you can use either Manual flash control or take advantage of i-TTL flash control.
Another option is to get a Pocket Wizard Mini-TT1 and Flex-TT5 (approx. $430.00 US) . Good Luck and Enjoy your Nikons!