YouTube member Wandomphoto performs a distance test with the Yongnuo RF603n (the n is for Nikon), and claims some pretty good results up to 1/4 mile away. These are very basic triggers and receivers that lack all the other high speed sync and communications that other high end triggers offer, but are fairly reliable. I am still using the RF602 triggers which included one remote trigger and one receiver. I haven't upgraded because they are not compatible with the RF603. The RF603 made a change in design that makes them 'Transceivers' which is both a transmitter and receiver. That's actually a much better design when you need to keep adding another remote or another receiver to the kit. A pair of these will run you about $30 bucks, and you can check them out via eBay (click here)

Yongnuo RF603 Wireless Trigger Receiver