Information about the frequency deviation is critical to reliable and stable operation of the power grid. Current wide-area power grid monitoring systems consist of Phasor Measure-ment Units (PMUs) at both high-voltage transmission level and low-voltage distribution level, but are generally unsatisfactory for large-scale deployment over highly distributed microgrids in individual households and local communities due to their high cost and low accessibility. In this paper, we present a practical system design which significantly improves the accessibility and reduces the cost of frequency monitoring by unleashing the capabilities of modern mobile platforms in computation, commu-nication, and storage. In our system, the Network Time Protocol (NTP) is exploited for time synchronization, replacing inflexible GPS receivers that are widely used in current PMUs. A small quantity of peripheral hardware components are used to build up an embedded sensing component for efficient and accurate frequency measurement. The experiment results compared to the traditional Frequency Disturbance Recorders (FDRs) show the effectiveness of the proposed frequency monitoring system.