If you're using the Revenue Cycle Modeler, you can apply an SLA of 1 day to leads and then track the overall percentage that violate the SLA over time. On a macro level this works quite well.
On the micro level, the best way I've seen is to set up a smart campaign to send an alert if the status isn't changed within 24 hours. This might go to the salesperson and yourself, and their manager. This is easier to implement because it behaves more like a stopwatch and the alert creates an action at that moment. You might also add them to a static list if you want to view over time.