Are you talking about the electronic dosimeter or the card? Because I would think the card could be used perfectly clandestinely - slip it between other cards, "forget" it in your pocket, don't look at it until after you're done with the gestapo. Post the readout on the internet ASAP and instruct readers to spread it far and wide, making sure to post it on websites hosted in lots of different countries so it can never be taken down.

Aside: Gestapo. GeSTApo. ...can we put in for special dispensation from the linguists at Oxford to allow for spelling it "geTSApo" until this whole mess is over?