Symbol keyboard

I think there is a niche for a touchscreen keyboard that acts as an auxilary to the existing keyboard and displays symbols and characters that are not on the standard keyboard. Being a touchscreen, the symbol keyboard could easily be reprogrammed with different sets of characters that the user needs at their fingertips - a set of shortcut buttons would allow the user to switch between sets of symbols (either predefinied e.g. "maths" or user-defined).