Of course, the most practical solution might be to have a chip
embedded in your arm, as they do with many pets these days. Then, not
only is there no chance of you losing your ticket or leaving it at
home, but you also cannot fraudulently transfer it to anyone else.
Furthermore, if you ever got lost and insensible, they would know
where to return you. It could also be updated while you were having a
bath by passing the signal down the water pipe.