This is a retro of MachWave mobile application written on June 26th, 2014. The Objective-C, source code for iOS is now on Github. However, the application is no longer available on iTune for download. This camera application has a custom view that supports 2 lines being drawn via touch-points (below).
When there are four touch points, two lines are drawn. Tt calculates the mach number base on the touch point coordinates and intersecting angle. The values are posted at the top of the photo (below).