Roll Ruler app for iPhone and iPad
Yes, I know that there are already some apps which can turn ios device into a measure tool like a ruler, i tried some of them, really not that useful, because iphone is TOO short to be a good ruler.
on the other hand, this app, can measure lengths in a better way, just roll your device along the line/object you want to measure and there is what you want.
hope it will be useful for you~
please note that this is an old app, so it just work well with iPhone 4 and iPhone 4s .