You could have downloaded Regulae 1.0 for Mac from our software library for free. This free software for Mac OS X is an intellectual property of Serge Thibault. The application is included in Productivity Tools.
From the developer:
Regulae is a tool that allows you to measure items on your computer screen.
You may want to check out more Mac applications, such as LampStealer, which might be similar to Regulae.