This happens due to the method of Photoplethysmography Neebo uses to measure your child’s Heart Rate (HR) and Oxygen Saturation Levels (SpO2). It requires only a few optoelectronic components: a light source to illuminate the tissue (e.g. skin), and a photodetector to measure the small variations in light intensity associated with changes in perfusion in the catchment volume. This means readings can be made on virtually any surface. The "clothespin" is used on medical equipment for that reason, in order to prevent sensors being placed anywhere else other than the skin.
In order to avoid such cases, please turn off Neebo while not in usage. You can do it by going to App’s Settings and tap “Turn off” button at the top left corner.
We are also working on a solution which will prevent that from happening by introducing crosschecking using data from the other sensors Neebo has to verify that it is currently not on the skin.