Such an App would have to be an integral part of the video/picture recorder in order to be authentic, else, doing that after means altering the video/picture, no?
It would have to be a special type of camera, that is.
With the 'Location' feature turned on, and data connection available/active, modern smartphone embed GPS coordinates in each photo they take[1].These phones, depending on the settings, even have a timestamp on the media created. Many modern digital cameras also do this. So you can rely on the EXIF[2] data manipulation tools to do stuff like you discuss, BUT when you say 'certification', what exactly is the legal definition of that??
Going by the case you have referred to, I can only say that it's possible to accept the video recorded at the Jamhuri Day celebrations as legit - until one goes to court and makes a claim, using it as supporting evidence, upon which the courts will be easily manipulated to dismiss its legitimacy!
So, until the (Kenyan) law tells us what this 'certification' entails, we're just groping in the dark. Till then, we have to wait for the time details come out to enable us program the App.Videos (even amateur ones) have been used as evidence the world over, but Kenya is special.