I believe when deciding the primary mode of action, you should see what is the main function and what is the secondary function. The primary function of the digital pill is to deliver the mental illness medication and the sensor is a secondary and meant to assist the drug delivery. I believe this falls under the CDER department in the FDA. A failure in the sensor is an inconvenience and maybe a waste of money but it is not catastrophic. A failure of the medicine delivering can cause severe damage to the patient and can ultimately lead to a patient hurting themselves or others. The main goal of this pill should be to deliver the drug and therefore it should be in the department that is most suited to make sure that will happen.