Time Converter

The Time Converter was a handheld device possessed by Sarah Jane Smith. It allowed the detection, opening and closing of time fissures where the Web of Time was thin. Fearing she might use it to alter her timeline as she had recently, Sarah Jane destroyed it. (TV: The Temptation of Sarah Jane Smith)

Behind the scenes
The Sarah Jane Adventures website describes its origin as unknown and says the Converter could "manipulate time energy in order to create time fissures between fixed points in time. But be careful; these time fissures are very temperamental and could shut at any time!"