The Griffin Stompbox is a solid, wired foot pedal with a real stomp box pedal feel. In addition to four stomp buttons, it includes a 1/4" input jack for an optional expression pedal.
The Stompbox connects to your iPad or iPhone with a 30-pin dock connector. For newer Lightning port devices, you will need to use a Lightning to 30-pin Adapter.
OnSong lets you choose different actions for each foot pedal using the Foot Pedal Setup Screen. Just be sure to swipe to the Griffin Stompbox screen to enable the Stompbox and configure the buttons and expression pedal.