Marko! Polo! Marko! Bang

It may be the case that sympathizers with Ukraine are able to get physically close to Russian equipment, but not for such long times that they could sabotage it. For those individuals this device would offer an alternative. This marker round could be activated and then covertly directly stuck on, thrown onto, or shot at a piece of equipment. For example someone in a crowd a tank is going through might slap it on, especially if the crown is rowdy. The device would generally do nothing but force the owner of said equipment to perform sweeps for it. But on a preset schedule it would start emitting an unmistakable radio signal for precision munitions to home in on. The signal could be changed on a rotating basis to avoid replication. To prevent incoming round spoofing it may also be possible for the device to accept a secured signal to respond to from its own small onboard one time pad. Limitations in size and weight are obvious, and of course it would be extremely dangerous to be caught carrying one. But it's less risky than being caught with a wrench under a T-90.