For about $70 not counting batteries and box, you can build a RF remote shutter release with substantial range. It even has a rotating security code! :-)

Obviously, if you want to try this at home you do so AT YOUR OWN RISK. I am sure that it could void the camera warranty. However, it seems pretty safe to me ... you are just using relays to do what the remote shutter switch does.

See the first picture to links to the parts. (I have no financial interests in these products).