Mobile HTML: dial a phone number via a hyperlink

As HTML5 is becoming a really cool way of developing applications for the major smart mobile platforms (iPhone, Blackberry, Android, Palm Pre, all of them Webkit-based), it would be nice if one could invoke the dialer. It turns out, you already can, via URLs such as tel:+49/89/12345. Dots, slashes and a prefixed plus are all handled corrrectly. SMS URLs and Skype URLs are also possible.