for the iphone/ipod touch, there are some osc applications available.
have someone experience with e.g. the hexler touchosc application and linux. i mean is it possible to get botch working together.
http://hexler.net/software/touchosc
maybe people which ever used the capacitive touchscreen from a ipod/iphon can be envisaging that this can be a real powerfully, professional and at least cheap tool to control ardour.