In addition to performing SSH-agent and SSH-add tasks, it can remove all keys from the agent after sleeping or a minimum period of sleep, when the Apple keychain is locked, or when a screen saver is detected. It can also add keys whenever SSH is trying to use the agent with no keys on the chain, or when the Apple Keychain gets unlocked.
You have the option to enable a status bar item and disable dock items. SSHKeychain can store the passwords for private keys in the apple keychain. It can set the SSH_AUTH_SOCK variable used by SSH-add and SSH globally, so you can use it with all your programs.
SSHKeychain also has tunnel support.