Don't quite know what you need to do but you could have a look at using zenity. I've tweaked a few scripts but not built one from scratch. It looks similar to win32 dialog-script before visual studio turns them into GUI dialogs for you. The buttons can then call scripts or in your case possibly programme-functions.

Are there any GUI classes in SDL that could be used to make your menus etc? If so, just be careful with font-size and word-length - at least you know which device it's aimed at - not like pc software!