The boobie, planet or Pod (as they are called) are really useful for many things. I have them on all of my bags, although I have "rogue pods" which is an independant designer that makes pods for Balenciaga bags (do a search many of us have them). Anyway as for your question: I used mine mostly for coins. I live in the city and have to park at parking meters a great deal - I store all silver coins in mine. When I need a coin its right there on the front of my purse, easy to get to!
Love Pods!!!