It sounds like you want some degree of automation; the ability to make random targets pop up at random intervals maybe? Or a non-random delay sequence?
If that's the case then you would need some kind of programmable device with long range wireless comms.
Arduino is a common entry-level programmable device that could do what you want. There's also PIC microcontrollers which are much cheaper, but require more upfront learning and hardware design. You could also look into Beagle Bone, Raspberry Pi, et. al.
For the long range comms, there are several zigbee/xbee modules that can easily go to 2km and much further
https://www.sparkfun.com/pages/xbee_guide