I've added a sidebar item with links to some android apps that you may find useful. There are many, many more than the ones listed here. Remember that not all apps are "official" and some may come with fees associated with it so read things carefully. There are apps also available for Iphones and Blackberrys...check the sites where these apps are available for download.
I've listed the 2 official Weight Watchers apps and the unofficial WW barcode scanner (all of these are free). The official WW ones require you be a meeting or online member. I listed one of many unofficial WW tracker/calculator that is available. Once at the market just run a Weight Watchers search and everything will show up. Read descriptions because the program is slightly different in other countries and you don't want to download the wrong thing. But for most parts these apps can be very helpful.
Apps are also available for exercise, shopping lists, recipes and such....Enjoy!