Nice app. PIN lock is obviously very necessary and the app allows only 5 bad PIN entries. The timeout before the app locks and requires the PIN afresh is also selectable. This app is the perfect companion to CardStar which keeps barcoded cards, but does a sucky job on other cards. This app does a very nice job on other cards (including dealing with the flif side of the card), but doesnt do barcodes.
The only quibble I have with it is that the cards, once entered, cant be reordered or sorted in any way. Thus, if the app sorts one of your most-used cards to the bottom, theres no way to remedy that besides delete all the cards one by one, then entering them again in a different order. I think the way the cards appear is in order of being added. Also, there is really no text field allowed, so "naming" the cards is impossible. You see the upper edge of entered cards, and thats it. So, if you have two cards that look the same but one is for you and the other for your spouse, you wont be able to tell which is which.
Adding these two features would make it a 5-star app for me.