Is it safe to take photographs or videos of the eclipse using mobile phones or conventional cameras?

No, never without the proper protection. Pointing a camera or mobile phone lens directly at the Sun without an approved neutral-density solar filter can melt or irreversibly damage the device’s sensor in a matter of seconds. Furthermore, if the camera has an optical viewfinder, the concentrated light will cause serious burns to the human eye. Special filters (such as Mylar or Baader film) must always be placed in front of the lens, never behind it.