When I first got my D90 I took it apart and installed a home designed and made RF flash trigger that worked with CLS. As far as I could figure out it was the first one to be compatible with CLS TTL mode. I used some low cost RF modules that were tinier than I could make myself as the RF portion and designed the interface and modulator for the pulse position data transmission Nikon use for CLS TTL. Those same $5 modules could be used much easier for remote shutter triggering. My remote flash links work outdoors for about 50 meters reliable and 100 meters if the location is really optimum.
Another question comes up, if you are shooting sports with remote, you will likely need wide angle to be sure to capture the action with a fixed camera position. You would need to set it to MF mode and manually set the focus for the spot the action will be and not rely on AF which needs you to select a focus point. If you can get a camera on a tripod on the field, good luck but I would be surprised the venue would allow a free standing tripod too close to the field of action. What about a good telephoto lens instead, so you can get the nice compression effect, besides retaining control of the camera orientation and settings? Stan St Petersburg Russia