I don't think anyone ever recommended that you store your wallet in MtGox long-term, either, but a whole lot of people did it and it's not like when that went sour everyone said, "Oh well, it was stupid of us to trust Mt Gox!"
Also, the fact of the matter is that this is subject to the problem that every person everywhere can secretly try to attack every wallet everywhere. One person getting their (physical) wallet stolen when they go out is upsetting for that person, but if someone figured out a way to steal 30% of all peoples' physical wallets at once, you can imagine that would be seen as a catastrophe, which is exactly what you're looking at given the monocultural nature of software. Maybe it wouldn't be a problem for someone who knows the risk and knows what they are doing, but those people don't need the convenience this app purports to offer anyway. Best of luck, I hope I'm wrong.
Also, the fact of the matter is that this is subject to the problem that every person everywhere can secretly try to attack every wallet everywhere. One person getting their (physical) wallet stolen when they go out is upsetting for that person, but if someone figured out a way to steal 30% of all peoples' physical wallets at once, you can imagine that would be seen as a catastrophe, which is exactly what you're looking at given the monocultural nature of software. Maybe it wouldn't be a problem for someone who knows the risk and knows what they are doing, but those people don't need the convenience this app purports to offer anyway. Best of luck, I hope I'm wrong.