I had a kit which was able to switch pretty much anything at home. Mine was connected to an outside light which illuminated when I went onto the drive.
That overcomes the legitimacy of having it fitted to a car.
The second issue is the part where it is less than ideal to interfere with police radio transmissions.
The device I had catered for this by having a feature built in which would automatically 'pause' the transmission if another device was received. Another useful function was that it would sound an audible warning in the car. This might, under the right circumstances, cause you to reconsider your speed
I'll see if I can find details.