If the device - about the same size as a ticket stub - is not within range, the Panasonic mobile phone automatically locks and, perhaps more importantly, can be located using satnav technology as and when required.
NTT DoCoMo claims that users can set the stub to lock their phone if they move more than eight, 20 or 40 metres away from the handset.
If course, if a thief gets their grubby hands on the stub as well as the handset, you're a bit knackered.
Not to a vast extent, though, as NTT DoCoMo says the phone has a facial ID lock that will only allow access to its database and contacts information if it recognises you.
All clever stuff. As the handset won't arrive until next month, NTT DoCoMo isn't saying how much this amazing gizmo costs...