The Dragon Radar was originally created by Bulma
to help her pinpoint the locations of the 7 magical Dragon Balls
which legend said once collected together would grant the user one wish. Bulma bumps into a young boy named Goku
who turns out to have one of these Dragon Balls. The two then go on an adventure to find the other balls.
In video games the Dragon Radar has been used and referenced to many times. In some games there are minigames using the radar in some way. In Dragon Ball Z: Budokai
it was used as some of the games menus. It was actually put to use properly in the PSP game Dragon Ball Z: Shin Budokai - Another Road
as it was actually used to find the Dragon Balls on the ground or see which of the enemies and allies on the map were holding Dragon Balls.
The button on the top of the Dragon Radar is usually used to zoom in or out on the screen. It is useful to zoom in for example when a Dragon Ball is only a few feet away, whereas its handy to zoom out when a Dragon Ball is miles away. The range of the Dragon Radar seems to be unlimited. In Dragon Ball GT, the Black-Star Dragon Balls are scattered all over the entire universe and the radar can still pick them up even with countless galaxies between the Dragon Radar and the Dragon Balls. It has never been stated whether or not the same Dragon Radar is used for the different sets of Dragon Balls, the different sets being the original Dragon Balls on Planet Namek, Earth's normal Dragon Balls and Earth's Black-Star Dragon Balls.