If you use the API Test Kit to check your water parameters and have Android, I found a really neat app that will help you. Best of all, it's free. ($0.99 for a paid version to support the developer).
It's basically an app with multiple timers. You can save them, reset them, run them simutaneously, lots of cool features. I use it every time I test my water (and for new fish acclimation (don't worry, that's 1 cup of aquarium water every 10 minutes for an hour
App is called Tom's Multi Timer Free
See attached for a screenshot I took in the middle of one of my water tests.