I think the Customs issue is over egged, you can import equipment than runs on any frequency (legal or illegal) its only when the end user trys to use it, that it becomes a problem. Thats why there is so much junk being sold on E*ay that is illegal to operate in this country, mobile phone enhancers, cordless phones using the wrong frequency, GPS & GSM blockers, etc.
2.4GHz will be limited to line of sight for any decent distance, remember that a receive antenna high up off the ground will give better results.
If you were to use WiFi cameras and technology you would be able to use some routers and access points as a hop site, which if installed in a tree for example would give you a greater transmit distance. For example ground buggy to tree (short range) then tree to house (long range).
2.4Ghz camera systems may also be able to receve and retransmit via a hop, but I haven't seen any as of yet.
Just my thoughts on the subject.