Android App to create a real-world like ruler for taking measurements

Imagine you're an employee of Measure Corp. Your job is to measure things, but you don't have any rulers because Measure Corp just sold it's last one. You do have your computer, and your android phone - and you know that you can use your programming skills to create a reasonably accurate ruler on the screen of your device.

Create an app which displays a ruler. The ruler should be as accurate to real-world measurements as you can make it, and should display inches, half inches, quarter inches, and so on. Optionally, your new ruler view could also provide touch feedback to allow you to measure things using your finger.