If you have an iPhone, Livid Instruments Guitar Wing looks like a good solution.
http://lividinstruments.com/products/guitar-wing/
One other idea is to use a MIDI controller keyboard, not for playing the keys, but just to send program changes. These keyboard controllers are inexpensive, portable and can store a programs that have multiple parts on different MIDI channels with Program Changes and other MIDI messages.
The only other option is to choose a "foot" pedal like the Keith MacMIllen Soft Step ( with the KMI Expander to connect directly to MIDI 5 pin Din) and use it with your hands.