are you on v2.0? You don't need an app. Just touch and hold the image you want to save and a popup will appear giving you an option to save the image. The image is saved in your camera roll.
i dont know where that app is , but dude if i was you i'd stat with 1.1.4. that was the best.i have the 3g iphone. i might trade down with someone, all the best apps are with 1.1.4.