A system (10) that can be used to retrofit any machine (15) for indicating when to perform maintenance service tasks for the machine (15). It includes a service tracker (12) connected to the machine (15), and also a maintenance manager (14) typically hosted by a hand-held device and coupled to the service tracker (12) by a wireless link (12a 14a 16), so as to allow providing a service interval for each of typically several tasks. For each of the tasks, a timer (42a), preferably resettable via the maintenance manager (14), is provided as part of the service tracker (12), allowing direct comparison of a service interval for a task with the reading of the corresponding resettable timer (42a). Based on the direct comparison of service interval and resettable timer reading for a task, the service tracker (12) provides a service warning via a display (12d) when it is time to perform the task again.