Electronic Circuit help

[FuNkShUi]

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[indent]Hoping I could get some help from some people with more experience in circuitry design. Won't be hard as I don't have much at all!!
I don't know if this is something you could help with, and no problem if not, but it could be really useful to me, so any help is certainly appreciated
Aside from Bass guitar playing, I am involved in dog training, and one of the issues I have is knowing a dog is, or has been somewhere (a certain contact point) whilst either I am not there, or they are too far away, or moving too fast for me to see. Would be useful in obedience work and working dog trial training.
Let me give you an example, I'm training a sheepdog to move to a certain place, but from 800m away. I want to design a circuit that will show me that the dog has stood on the point I'm asking. So maybe a light will illuminate to show me. The output doesn't have to be a light, but can't be a sound, as i don't want the dog to notice it if possible.
The proviso's would be that it would need to be thin enough not to protrude too far out of the ground. I don't want the dog to notice it basically, otherwise it will be learning to target the contact sensor rather than just listening to commands.
I only need it to show contact. It doesn't need to show varying strength of contact, just on or off (contact met or not). Obviously need to reset it too, and I don't want to be trekking out 800m every time to have to do that if possible.
After a little research, I thought a way to do it would be to use a FSR. Mounting four of them on the concerned "contact area". One in each corner, with a small actuator attached to another thin flat hard but flexible material above. That should ensure the design is thin. So I could bury it under some soil with minimal fuss.
How would you go about setting up a circuit for this? The simpler the better, as I said, I am a beginner.
Thanks in advance for your help [/indent] [indent]If this needs to be somewhere else, i'm happy for it to be moved.[/indent]
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[markstuk]

would not some form of gps collar/transmitter with your contact areas co-ordinates mapped in not work better?

[FuNkShUi]

It doesn't prove they have put their feet exactly on the contact area. Unless there is a way i could do this that i don't know about?
I need it to "prove" that force was applied to that specific contact zone, no matter how briefly.
I was also thinking of a reed switch, but i think that might be too big

[Grangur]

Proximity sensor maybe? Or would that maybe, being too selective on actually hitting the spot?

Perhaps some added info on what exactly the doc ix ment to do when it gets to 'the spot' would help? Is it a case of hos left front will be on pad A and the right will be on pad B? Or is it not that accurate?

[FuNkShUi]

Not entirely that accurate. There is a pad on the floor (they range in sizes) but lets say this one is 900cm X 400cm.
The dog has to make contact with them, with at least one paw. Can be more too though.
It can touch it by running over it, so only briefly depressing the contact. Or it can do a dead stop on them.