In case of "SIN GLUTEIN" or anything, make a small label
with spanish translation of what you want to be without.
Question of glutein was never a problem, but to show the label
seemed to be a brilliant idea.
Similar functios seems to be available for mobile phones.
An additional gadget is not necessary. Many of these programs are for
commercial distribution network to see where cars are going.
And drivers try to hide the phone to get some liberty moments.