The 'alarm charm' was designed as a system of 4 items (a handbag charm & 3 smaller charms to go on valuable items) to help in the fight against pickpocketing.
The theory of the system is that pickpockets thrive because victims are unaware of the theft until it's too late and the thief relies on their 'normal' look to give them total anonymity when in public.
The 'alarm charm' notifies the user when an item is taken and can identify pickpockets as thieves, even in crowded situations. The system would also work if the user would usually have lost the item through fault of their own (e.g. if leaving their purse at the checkout).
The charm is designed to be worn on the outside of bags to act as a visual warning and deterrent to pickpockets (that want easy targets); while also encouraging people to take care of their items, by folding out into a handbag hook to keep bags in sight of the owner and not under tables or on the backs of chairs (where they're easy targets to a pickpocket).