You have your own reasons to keep certain photos from others' eyes. Private Photo Vault by software developer William Sidell lets you store your photos in a secret gallery. This free app lets you select photos and videos you want to keep hidden by passcode-protecting them. During setup, after you punch in your four-digit PIN, the app prompts you to email the passcode to yourself because if you forget the passcode, you are completely locked out of the private repository.
Once you're in your secured vault, you can create slideshows and export, delete and move pics. Using the wireless sync feature, you can upload photos from your computer straight to your private vault. In addition, you can create multiple private albums and password-protect albums individually. Private Photo Vault runs on iPhone, iPod Touch and iPad and needs iOS 4.3 or later. The $2.99 Pro version gives you the option to establish an onscreen pattern as a passcode instead of a PIN.