A team from the University of São Paulo in Brazil have developed an open-source solution for monitoring marine habitats. The device, known as a Passive Acoustic Monitoring device, is a sonic spectrometer which measures underwater audio signals and records them, thus allowing researchers to analyse the data and detect both marine wildlife and human-made sound disturbances. The device, which uses a Raspberry Pi model A to record data onto an 128GB SD card, costs an estimated $500, which is about a 1/6th of the cost of other commercial offerings. Read more about this over at the Raspberry Pi Foundation or read the original paper from the Brazillians.