Gearoid was an Android emulator for
Sega Master System and Game Gear games, developed by yongzh, that was originally a paid application but later offered for free on the SlideMe appstore, though it is now no longer available. To use a similar emulator, you would need to find an alternative for your Android device, such as one of the many options available on platforms like the Google Play Store or other emulators mentioned in discussions of retro gaming