All of our GPS products include a temperature sensor.  Traditionally we use that sensor to record one reading with each GPS position.  Then one day a customer explained that he was putting external temperature loggers on their study animals and it was adding a bit too much weight. 

Our customer asked if we could just create a feature whereby he could utilize the temperature sensor as a logger.  Of course that was not going to be a problem, we agreed to do it at no charge and now it is a standard feature on some of our products.  

The sensor is fully user programmable to record temperature at the times the customer needs.