Inhaler Data Logger...Not sure if it's a "wearable" but I will go with it for now. The idea is that there are some types of prescribed medicines that are taken "as needed;" not on a schedule. One example would be an asthma inhaler. The only quantifiable data that can be collected about usage is that some have a mechanical counter built in to tell you and your doctor how many doses you have left. But if there was a low-cost, low-power data logger, then it's possible that usage trends could be found. For example, the data could be later compared to: the pollution levels or pollen count for that day; weather conditions; or when your cat is shedding fur the most. It could also be used to help detect improper inhaler technique or damaged inhaler by showing trends in too frequent doses, etc.
Asthma inhaler is the first thing that could to mind but this could be modified for other "as needed" medicines; such as anxiety disorders. For oral medications, a pill box could be modified to detect the lid opening. Of course, this might be a helpful build for a loved one who has to take scheduled medications but you're unsure they are remembering to do it.
