Pro Compass is an iPhone app developed by Craig Hunter that replicates the look and feel of classic pocket compass hardware from the 1800s. It offers modern features and technologies, such as advanced OpenGL graphics, to render 3D floating compass hardware for realistic operation.

The app includes nine different compass modes with direct read, traditional, and rosette styles capable of displaying degrees, quads, or mils. Pro Compass shows both magnetic and true direction simultaneously, with a rotating outer true ring that adjusts for local magnetic declination. The app also displays location and altitude in decimal, degree-minute-second, UTM, and MGRS position formats, with an optional "Datum Pack" that adds over 230 geodetic datums covering regions and countries on all continents around the world. Additionally, Pro Compass contains a built-in two-axis inclinometer that drives two independent bubble levels and a bullseye level.

It's important to note that Pro Compass reports accuracy directly from the magnetometer sensor in your device. To improve results, operate Pro Compass away from any electronics or other sources of electromagnetic interference. Overall, Pro Compass is the best and most realistic compass available on the App Store.