Would be nice to have some of the functions, which are included in the Canon Hack Development Kit (CHDK):

-Zebra Mode (shows areas in the picture which are too bright / dark)
-Live Histogramm (shows frequency of colours in a graph)
-Remote access (could be by USB / Bluetooth / IR, Call, SMS or maybe as a Webcam by Wlan)
-Script support (motion detecting)
-HDR and longtime duration support