This thesis presents the design, calibration, and performance evaluation of a type of two-hole pressure probe anemometer known as a Conrad probe, as well as its subsequent implementation on an autonomous, compact boundary layer measurement device and its first application for subsonic in-flight measurements of a swept wing boundary layer. Calibration of the Conrad probe was accomplished using two calibration functions and a non-nulling method for resolving in-plane flow velocity direction and magnitude over a range of ±30 degrees. This approach to calibration and application offered the advantages of rapid data acquisition with lower energy consumption than alternative methods for pressure probe anemometry in swept wing boundary layers. Following calibration, the probe was adapted for use on an autonomous boundary layer measurement device including development of revised software. Utilizing this setup, boundary layer measurements were obtained on both swept and unswept models in a wind tunnel with a maximum operational velocity of 110 mph corresponding to a dynamic pressure of 30 psf. The wind tunnel results showed that the Conrad probe could measure in-plane flow magnitude for both laminar and turbulent boundary layers with sufficient uncertainty and spatial resolution for its intended application in flight testing. The Conrad probe and boundary layer measurement system were then employed for flight tests of a 30 degree swept wing model carried beneath an aircraft at a flight Mach number of 0.52 and altitudes up to 44,000 ft. The flight test results from the Conrad probe allowed for the successful determination of overall boundary layer thickness, laminar/turbulent conditions, and degree of flow turning within the boundary layer. It is believed that the rapid data acquisition and low energy consumption of the Conrad probe implementation on the boundary layer measurement system make it a good alternative for future flight testing requiring measurements of in-plane flow velocity magnitude and direction.