Abstract: Methods and apparatus for providing a device, such as a treatment device, on a pay-per-use basis are disclosed. Generally, a wholesaler supplies a treatment device to a retailer. The retailer pays the wholesaler on a per use basis, which is regulated by a digital key, such as a smart card attached to the treatment device via a smart card reader. When the value of the digital key drops below a threshold (e.g., only ten treatment sessions remaining), an alert is generated by the treatment device. When the value of the digital key is reduced to zero, the treatment device does not operate until the digital key is replenished or replaced.