Abstract: An overdose of opioids can cause the user to stop breathing, resulting in death. A physiological monitoring system monitors respiration based on oxygen saturation readings from a fingertip pulse oximeter in communication with a smart mobile device and sends opioid monitoring information from the smart mobile device to an opioid overdose monitoring service. The opioid overdose monitoring service notifies a first set of contacts when the opioid monitoring information indicates a non-distress stats and notifies a second set of contact when the opioid monitoring information indicates an overdose event. The notification can be a phone call or text message to a specified person, emergency personnel, or first responders, and can include the location of the smart mobile device. The smart mobile device can also include the location of the nearest treatment center having emergency medication used in treating opioid overdose, such as naloxone.