in *nix, you got three choices I know of for making a frontend. Gtk (Gimp Tool Kit), TK (a graphical extension of TCL) and QT (the KDE gui toolkit, I should look it up so I know what it means :p ). I know a bit of Gtk, I'm using it to give my IRC client a gui (writing client in perl, therefore using Gtk-perl). As for the others... *shrugs* TK is cross platform, but if you are using a *nix utility then this is a moot point.
So far my experience with Gtk is good. I found it remarkably easy to figure the basics out and get something working.
An example of what Gtk looks
like. </blatant plug>