Features for assessing patient compliance with therapeutic usage of an inhaler, such as a nebulizer, are disclosed. Nebulizer therapy accessories include mouthpiece, mask and adaptor (i.e. an attachment to a mouthpiece or mask) that may be coupled with the nebulizer. The nebulizer therapy accessory includes at least one sensor that detects a physical parameter generated by a user's body and generates a signal. The signal is used to determine therapy compliance, which may be communicated to the patient and/or the patient's physician.