What is the easiest and most accurate way to test your urine and/or
saliva for PH? Does it make sense to use a PH meter?

Do it yourself test strips are readily available from drugstores and
chemical suppliers. Accuracy for these differs depending on the test
range but is typically to the closest 1 or 0.5 pH unit. Metered
testing can obviously be more accurate, depending on the equipment and
protocols, but is more difficult to perform.