All good questions which I dont know the answer to :-(
We need to find someone who is an expert in them
I know I have seen them very flat - something like 3/4" square but I dont know if they would work wrapped round an arrow
Pets have them injected inside them but I dont know how big these are
I have just been trying to find info on the internet, but not much luck so far
I did find an electronics project for a home made detector but it doesn't say what range it has (looks cheap to make though)
http://www.elektor-electronics.co.uk...d=28&art=52705
The usual detectors would be expensive because it needs to read info from them, all we need is something which detects one is there (as this claims to)