Small low-cost instruments enable new and exciting mission opportunities yet their constrained volume and limited budgets make them especially susceptible to suffering anomalies during flight. Radiation effects as well as sensor or actuator failure can all pose a serious threat to the continued collection of scientific data as well as cause the partial or complete loss of a mission science payload. Onboard anomaly detection could allow instruments to recover from such events but its ad hoc development typically falls outside the mission timeline or monetary constraints. Here we describe a compact solution for the implementation of onboard anomaly detection meant for space science missions. The device is designed to be interoperable with a broad range of instruments utilizing easily accessible power and logic signals to monitor the state of peripherals and actuators without disrupting their functionality. By leveraging a commercially available microcontroller with a radiation hardened alternative package the device can be inexpensively sourced and assembled with minimal work enabling instrument characterization on an expedited timeline. The system can then be exchanged for a radiation hardened version ensuring the replicability of observed anomalies in a laboratory environment during instrument operations. We also present currently implemented anomaly detection algorithms which enable the system to detect anomalies in instruments with varying failure modes and allow mission designers to choose which detection approach best fits the specific needs of their instrument. Finally, we showcase an example application of this system in the detection of anomalies during the operation of a lysis motor designed for use in biological space instruments.