Ive been searching for one too, would be brilliant! i found one that could keep a tally and work out the points for WW although it was not an official version!
Ive even considered trying to learn how to make an app for SW as it would be fabulous - but where as with WW its a simple calculation to work out the point value, with our diet there are lists and lists of syns and there values, and the same again for the different options and the free foods - it would possibly take a huge amount of code to create, where as the good folks at SW will already have this for anyone else to re-create the level of detail needed it would take hours, which is more than likely why someone hasnt made it yet!
i might send a note via the SW website as i think it would be fabulous to have, and i would pay a £1 or so to have it on my phone, as it would make life so much easier than keep going on the website to update my diary!