This is a 3D model of a heart rate monitor that plugs into a 3.5mm headphone jack. This is designed to be used for people with disabilities and require checking their heart rate constantly throughout the day. It would be hooked to a keychain and be carried around then plugged in when needed. It would work with iOS and Android devices with a companion app. The person would plug it into their phone and launch the app, then they will hit the ‘start test’ button and place their finger in the crevice and the phone will receive the data to display. This is a prototype, and is still in development. If edited, please give credit. (there are plans in the future for this to eventually be built) MRK II 3D Printing: The optimal way to print this object is with the key chain loop faced down and the headphone plug horizontal. Make sure you turn the fan on during the bridging process (when printing outward) to prevent it from making ridges.