Problem: my dogs constantly counter-surf (stand on their back legs to get stuff off of the counter), but they're smart and only do it when nobody is around; it's very difficult to catch them in the act.
Before I try to implement some way of deterring them (but I don't want to shock them), I need to be able to accurately detect when they're doing this. Given their height, I think the best way would be to somehow detect when their collar is within 10 or 15cm of the edge of the counter.
I'd considered RFID but that would require readers every 20cm or so with their range/power turned way down.
Is there a way to detect when something is within a certain range of a linear device? I'd like to mount something under the edge of the counter top and when it detects a collar that's in its range, do something (in the short term, that 'do something' will probably be take a picture with a webcam.)