I certainly think it's an interesting idea, especially being able to see cop blips from further away. Do cops even use the cop radio tbh?
It would definitely need to be a time-limited and expensive device.
Cops mostly use whisper, shout or group chat which makes buying such a device a waste of money.
I'd say maybe you could add some spice to it like being able to chat on the radio as well, no innocent can buy nor use the device or if you buy it you instantly get wanted level or maybe no wanted level unless used.. etc
Also if the player got arrested with that device especially if it's bought from the black market, they should not be able to get it back unless they break the evidence locker.