I have an SB 800, SB900, and D700 Nikon cameras. The CLS system doesn't work consistently when I'm shooting groups or reception shots at weddings. I think I may need a wireless trigger system. What would any of you recommend
The SU800 commander is a good choice. The sensors in the flash need to point to the commander. If there is still a line of sight issue, remote the commander using the SC-29 cable from the camera to the commander. I agree with the comments about Pocket Wizard. The ttl support has a lot of caveats and if you just triggering the flashes in manual mode, you can use a $20 wireless set.
Line of sight optical triggers are well known to fail on occasion.
Even Joe McNally occasionally has the IR of his CLS system fail. I've seen his gear fail in person. David Hobby, the Strobist, even made a "commercial" with Joe where they make fun of the IR systems failing.
The serious pros use Pocket Wizards. It looks like a lot of them use the manual-only triggers, but Pocket Wizard makes CLS systems that use radio instead of IR. Of course, these TTL Pocket Wizards are very expensive.
Lots of enthusiasts use assorted "poverty wizards" that are much cheaper. I love my Cactus V, but they are pure manual control only. No CLS/TTL.
When you say your current remote triggers don't work, I'll assume you mean the CLS system, which is and infra red system built-in to those flashes.
The Nikon CLS system, being intra-red, only works if the flashes are in the line of sight of the camera. If they are around a corner, or behind your group of people the signal will get blocked.
You can improve the reception by making sure the infra red sensor on the flash is pointing towards the camera. Turn the body of the flash so the sensor points towards the camera, and then rotate the flash head to point where you want it.
You can also buy an SU-800 controller, which goes in the camera hot shoe. It too is infra-red, but will have a bigger range than the one built into the D700 pop-up flash, if that's what you're using.
If none of that works well enough for you, then you would need to use radio triggers.
There are some recommendations here: Recommendations for Wireless Flash Triggers
With most of the basic wireless triggers you must set the flash power is manually at each flash - there is no TTL or CLS integration. There are newer models starting to come on the market that do handle TTL and allow you to control it from the transmitter on-camera. For example the Phottix Odin system, which allows you to control multiple groups of off-camera flashes.