Short answer: No. The rhythm method is a method of NFP, but one that is out of date and unreliable.
Short answer: NFP and charting can help.
Short answer: Yes!
Serena's Sympto-Thermal Method is only one of many modern and effective NFP methods available. While we admit we are totally biased towards Serena not only for its method, but also for its couple approach to fertility, we are also big fans of the other available NFP organizations and their respective methods. We support you in your choice of NFP. The best method and approach is that which works best for you as husband and wife and your particular circumstances. There are various organizations that offer NFP services, among them here are some of the most well-known and established:
(observation of cervical mucus, other symptoms as well as basal body temperature)
(observation of cervical mucus)
Even we NFP service organizations can seem disjointed in our approaches to reach out you. Here at Serena we hope to build bridges as well as to establish some notoriety for NFP. For a more exhaustive list of NFP methods and fertility monitors , see this review by Sara Fox Peterson. While written from a Catholic perspective, her review is the one of the most thorough and helpful resources we've come across. All this said, in finding the method that suits you best, do your research! While we can attest to the sophistication and effectiveness of Serena's STM, we can't share that same endorsement for all other methods and monitors listed (we just don't know enough about them!).
Short answer: They aren't our first choice, but there are options.