You can cheaply (and easily) add an hour meter. Useful for keeping track of maintenance.
I added one to my whole home generator. One wire simply wraps around the spark plug wire and one goes to ground. That's all. 10 years later and it still works just fine.
2008 Jayco Eagle SuperLite 29.5
2014 F250 6.7 PSD 4X4, CC LB