An external pressure sensing system may include an attachment for a syringe. The attachment may comprise a connector positioned between the barrel and the needle of the syringe. A pressure sensor may be in fluid communication with the connector, such that the pressure sensor may sense the pressure of fluid within the connector as the syringe is used to add fluid to or withdraw fluid from an injection port. Where an injection port is a component of an adjustable fluid-based gastric band system, pressure data obtained with the pressure sensor may be indicative of the pressure of fluid within the gastric band. The pressure sensor may communicate pressure data to a display device. A user may adjust the pressure of fluid within the gastric band using the syringe while viewing the display device for pressure-related readings.