Secret Contacts
Whether you're pulling double-agent duty or simply trying to keep the identity of your "hoes in different area codes" away from prying eyes, Secret Contacts ($2) can help. Masquerading as an innocuous tip calculator on your iPhone's home screen, this little black book shows its true colors when you enter a secret bill amount into the calculator. Just make sure your significant other isn't an Uncrate reader, in which case this won't be nearly as sneaky as you think.