there are some things that i am not sure of: how far does those particullar signals travel, i think somehow they would have a smaller range then the regular plasterite…
maybe it is better to separate specific ingredients and cast them into a smaller pieces, with a few miles radius, depending how far one is traveling, so the idea was to tune in when you need your things (i think it is safe for others, as you would know what and where to request them from), in a way… i am not sure how to test it either… probably dowsing, will have to really learn that 
I think that will be interesting thing to try