Aren't you some kind of coder niall. if you can figure how to get that info I'll implement it. I thought of that feature too...i just didn't have any idea how to do that.
Instead, I thought about making it so users can set colors on the map to indicate if someone is farm-able or not. Then save those settings out to a client side cookie. Other options are save user's settings to a DB table or make a wiki-colaberative style map where everyone can color/note coords. I don't want to have a DB users account table to save those things...though if I get serious it might need user accounts. I'm just winging most of this coding without much planning ahead of time.
One strange thing about BP also. I ALWAYS get the same date/time message when trying to raid someone who seems to be under BP...I can only think that maybe you can't see the real date and only see your own BP end date? Not sure...