Controlling a simple RC vehicle at long dinstace from a PC
Long-ish range radios are becoming more readily available. Recently I used a few of these:

Digi 900mhz modules

They use the xbee footprint, so can be used easily with many arduino shields and other cheap hardware.

You can set two units up to be a transparent link. This can carry data via serial port, or it can mirror GPIO pins between the two. (I have used this feature on the 2.4ghz ones, but not these) 

If you set the master with an input, and the slave with an output, toggling the pin on the master should toggle the pin on the slave automagically 

Don't believe the 28 mile claim though! Line of sight with a high gain antenna might get you half that. Maybe.