A spot check credit system that partitions the task of distributing sensor credits between a server functioning as a credit provider and a plurality of clients functioning as credit requesters, the server and clients communicate over a computer network, the server runs a web server program so as to serve web pages to the clients, the clients run web browsers so as to receive the web pages and access spot check credits, the spot check credit system comprising: a server that communicates a plurality of web pages over a computer network, the server including a credit file application that executes on the server so as to generate a spot check credit file in response to a spot check credit request; a client in communications with the server and executing a web browser so as to receive the web pages, wherein the client relays the spot check credit request from the client to the server via one of the web pages, the request specifying a sensor ID and a requested number of spot check credits to purchase, wherein each spot check credit enables a single measurement for a group of physiological parameters, wherein the client downloads the spot check credit file from the server; a reusable sensor (10,2004) associated with the sensor ID, the reusable sensor being a noninvasive sensor including a light source and a light detector configured to output a signal indicative of light from the light source after attenuation by body tissue; a physiological monitor (700,2002) configured to communicate with the reusable sensor so as to perform spot check measurements in conjunction with the reusable sensor, the physiological monitor being configured to be in communications with the client so as to download the spot check credit file, the physiological monitor being configured to at least measure a blood analyte through analysis of the signals indicative of an absorption of light by tissue; and a device configured to increase an available number of uses left on the physiological monitor, the device including a photocommunicative key device for communicating spot check credits to the physiological monitor, the photocommunicative key device being configured to communicate with the physiological monitor through electronics of the reusable sensor. a server that communicates a plurality of web pages over a computer network, the server including a credit file application that executes on the server so as to generate a spot check credit file in response to a spot check credit request; a client in communications with the server and executing a web browser so as to receive the web pages, wherein the client relays the spot check credit request from the client to the server via one of the web pages, the request specifying a sensor ID and a requested number of spot check credits to purchase, wherein each spot check credit enables a single measurement for a group of physiological parameters, wherein the client downloads the spot check credit file from the server; a reusable sensor (10,2004) associated with the sensor ID, the reusable sensor being a noninvasive sensor including a light source and a light detector configured to output a signal indicative of light from the light source after attenuation by body tissue; a physiological monitor (700,2002) configured to communicate with the reusable sensor so as to perform spot check measurements in conjunction with the reusable sensor, the physiological monitor being configured to be in communications with the client so as to download the spot check credit file, the physiological monitor being configured to at least measure a blood analyte through analysis of the signals indicative of an absorption of light by tissue; and a device configured to increase an available number of uses left on the physiological monitor, the device including a photocommunicative key device for communicating spot check credits to the physiological monitor, the photocommunicative key device being configured to communicate with the physiological monitor through electronics of the reusable sensor.