I have had ideas to build a GPS based prototype on my own as a hobby project (both the hardware and software)... other than that I don't know of commercially viable ones.
However, in practice the cables are no issue - you can have them installed and dug in the soil rather trivially (the cable is shot in). Once done - you'd never notice them ever again. No go zone can be organized with magnetic strips (also buried).
However, in practice the cables are no issue - you can have them installed and dug in the soil rather trivially (the cable is shot in). Once done - you'd never notice them ever again. No go zone can be organized with magnetic strips (also buried).