An accessory (800) is provided for a mobile device (102) to measure characteristics of a test strip (808). The accessory (800) includes a test strip adapter (806), a phone adapter (802), and a coupler (804). The test strip adapter (806) includes a test strip attachment for a test strip type and a first interlock shared with other test strip adapters for other test strip types. The phone adapter (802) includes a phone attachment for a mobile device model and a second interlock shared with other phone adapters for other mobile device models. The coupler (804) includes a third interlock that forms a first mating pair with the first interlock of the test strip adapter (806), and a fourth interlock that forms a second mating pair with the second interlock of the phone adapter (802).