I had actually communicated with a company out of China that sold low end K band motion detectors for somewhat the same purpose.
I wanted to put them on the highway near where the mobile radar camera vans would hide out. I was thinking of using rechargable batteries and mounting them on a post just off the easement so it would not be considered littering (littering

).
I really think your idea would best be done via a RD or CM that is connected to the internet and gives GPS coordinates and a time line. The data could also be parsed out to show over a period of time the hideouts that the LEOs like.
If it were done this way it would be MUCH HARDER for LEOs to spoof like they do now with Trapster.
(But again some company would sell a device to LEAs that would look like a genuine device to our new found network and it's purpose would be to flood certain areas with falses to skew the data.)
I would bet that there are R&Ds working on interconnected Countermeasures right now.
COYOTE is coming to town. Merge COYOTE with a good CM set up and send all kinds of data to the net.
Why don't all of us pool our funds and build our own network? We could be very particular about where we get our info from... 