The "target" button don't seem to work on Iconia Tab A500, I need to plug a usb keyboard in order to target things. Is there an explanation or is it a bug ?

Thanks,

When you say "things" do you mean asteroids? Other players?

On Android the "target" button is set to target nearest hostile by default. You need to press, hold, and drag up if you want to set it to target in front etc.