Just how useful can a ruler app be on the iPhone’s 3-inch screen? Well, I guess it’s pretty useful if you have an occupation requiring you to measuring a kitten’s pinky toes. And who doesn’t love measuring a kitten’s pinky toes?

If you need to measure anything of significance though, you’ll probably just want to stop being ridiculous and grab, you know, a real ruler…

A quick check on the App Store will yield you a plethora of ruler apps that essentially do the same thing, and lots of them are littered with ads. The lack of ads and the fact that it’s freely available for jailbroken phones on Cydia, certainly helps put thRuler near the top of this niche genre.

Along with those positives, there’s also feature that will let you mark a spot on the ruler with a single tap, and remove the mark with a double tap. Something like this might be handy on a real ruler, but if you’re measuring something shorter than three inches, I would think you would be able to remember your spot pretty easily.

I suppose I could envision a few applications where such an app would be useful, perhaps while working on a car and you need a quick measurement, or in other situations where you need a quick rough estimate. Other than that, this app, and others like it are surely not a replacement for the real thing.

What do you think? Are mobile rulers, and things of that nature taking it a bit too far?