Abstract: It is provided a fastening device for temporarily fastening a portable sensor device to a human body, the fastening device comprising: a device holder for releasably holding a portable sensor device configured to capture electrocardiogram signals and audio signals; a skin sealer configured to form an essentially airtight interface with a human body; and a bellows provided between the skin sealer and the device holder, the bellows, configured to fasten the fastening device to the human body using a suction effect after a portable sensor device held in the device holder is pushed towards the human body to let air escape from the bellows via the skin sealer.