There are an increasing number of products on the market designed to indicate possible fertility. They rely on changes in hormones that can be detected in your urine or saliva. When using these kits and devices, the most important thing is to follow the manufacturer's instructions as closely as possible. Questions that relate specifically to a certain product are best answered by that manufacturer and most products have 1-800 numbers on the package to allow you to ask questions.
These kits and devices can give additional, secondary clues about your fertility status that can complement the observations you make from your primary fertility signs (cervical fluid and BBT). You may find them especially useful if you have irregular cycles, conflicting signs, occasional anovulatory cycles, or if you find that you are not able to get clear readings from your cervical fluid and BBT signs. In most cases such devices are not essential, especially if you are easily able to recognize the changes in your cervical fluid, but you may find you like to have the added information for cross-checking.
These devices generally detect increasing levels of estrogen or luteinizing hormones, the hormones that peak before ovulation. No device or kit that you can do at home can pinpoint ovulation as well as your temperature data since only a thermal shift shows increased progesterone which is the hormone you release after ovulation. They can be quite useful though for timing intercourse and showing you when you have increased fertility.
Fertility Friend's analysis supports (but in no way requires) the use of OPKs, the Clearplan Fertility Monitor and Saliva Microscopes. If the data points are entered, the analysis will make use of the data.