Advances in low-voltage integrated circuits have enabled the development of low-cost, low-power, and downsized portable instrumentation. In the biomedical field, mobile sensing platforms provide an efficient way to monitor the physical condition of a subject. Moreover, these platforms provide an input for human-computer interaction. We developed a low-cost platform that can be adapted to acquire different electrophysiological signals, and interface with portable devices for storing, processing, and displaying of data. The developed platform was used to acquire electrocardiography (ECG), electromyography (EMG), electroencephalography (EEG), and electrooculography (EOG) signals, and the results were compared with signals obtained with the benchmark BIOPAC system. For the same frequency bands, results show that our portable platform was able to acquire electrophysiological signals with similar accuracy as those acquired with the BIOPAC system. Due to its simplicity, low-cost design, and easy implementation, the developed platform suits researchers, developers, and hobbyists, in the fields of physiological monitoring, human-computer interaction, and perceptual computing.