An example of what slips into the news without critical examination: from the BBC, Scans reveal lost gravestone text. This is an interesting feature about work by the Ambient Intelligence Group at Carnegie Mellon University using a combination of 3D scans and image processing to recover eroded and/or overgrown texts. That's the good science. But there's an incongruous aside, mentioned twice: "The technique could one day also be used by doctors to examine a patient's tongue for signs of illness ... Dr Cai said: 'We may use the technology ... to ... help medical doctors to diagnose patients' well-being through tongue inspection'. Whatever's that about?
A little Googling finds it concerns A Novel Imaging System for Tongue Inspection (PDF). We're talking traditional Chinese medicine - TCM - which places significance on tongue diagnosis. This patent, Method of extracting region of interest from tongue image and health monitoring method and apparatus using the tongue image, shows a deal of work has been expended toward high-tech embellishment of this technique. Needless to say, TCM's detailed model based on the tongue mirroring various parts of the body and producing diagnoses such as liver qi stagnation or heart yin deficiency is not part of mainstream Western medicine.
Of course, it's possible that the overall edifice is daft but there still could be specific correlations between the tongue and some conditions; as Embarrassingproblems.com mentions, a smooth, red, sore tongue can be a sign of anaemia. Yang Cai is investigating, he says sceptically, the possibility that tongue appearance may correlate with cancer, providing a non-invasive diagnostic method. However, much of the preliminary evidence comes from Chinese partisan journals such as the TCM Diagnosis Association and China TCM Society and, unfortunately, China is one of the places where published clinical trials almost invariably report positive results. So it's probably best to wait until it appears in the BMJ or similar.
More about the story at Carnegie Mellon Magazine: East Meets West / Tongue Tells Health Tales.