Game : https://itunes.apple.com/us/app/1010!/id911793120?mt=8
Needed: jailbroken device and gamegem
Steps: go to 1010 and get a score, then open gamegem type the value of your score press the search button and go back to 1010. Get a new score in the same game, go back to gamegem and type the new value, press search again. A new button should have appieared, click it and change the value for a high score( max 999999) then go back to 1010 and close your device( do it or it will not work idk why) wait open your device back.
Enjoy
A good gamegem tutorial: https://youtu.be/Xr0sl4tVHkM