This work presents a palm-sized, cost-effective biosensing device that integrates an enzymatic paper biosensor with an Internet of Things (IoT)-enabled smartphone alert system for fluid-based alcohol detection. The device consists of a paper-based sensing platform, a potentiostat-free data acquisition system using commercially available electronic modules, and an IoT-based wireless alert that notifies the user via smartphone when their blood alcohol concentration (BAC) exceeds the legal limit. The biosensor utilizes alcohol oxidase (AOx) as the catalytic enzyme, immobilized on filter paper and stabilized by bovine serum albumin (BSA). Both electrodes are fabricated from widely accessible materials: aluminum tape as the cathode and graphene–nail polish ink as the anode. Housed in a compact, 3D-printed enclosure (3 × 5 × 5 cm³), the device achieved high electron transfer efficiency with an internal resistance of 10 kΩ. It exhibited a strong linear correlation (R² = 0.9798) across a range of 14.02–88.45 mg dl⁻¹ (sweat-calculated BAC) and 20.70–119.14 mg dl⁻¹ (saliva-calculated BAC), with detection limits of 7.82 mg dl⁻¹ (sweat) and 12.51 mg dl⁻¹ (saliva). The device demonstrates sensitivity across BAC levels from the mild impairment threshold to above the legal limit, with high alcohol specificity. It provides a portable, cost-effective solution for fluid-based alcohol monitoring in low-resource settings.